Laminated ferrimagnetic thin film, and magneto-resistive effect element and ferromagnetic tunnel element using this thin film

ABSTRACT

A laminated ferrimagnetic thin film consists of two ferromagnetic layers and a non-magnetic intermediate layer sandwiched therebetween. The respective ferromagnetic layers are magnetically coupled in an anti-ferromagnetic manner through the non-magnetic intermediate layer. Each ferromagnetic layer consists of a plurality of layers. In each ferromagnetic layer, a layer which is in contact with the non-magnetic intermediate layer is formed of Co or an alloy including Co while at least one layer is formed of Ni or an alloy including Ni, and its film thickness is determined to be at least 60% or more of a film thickness of each ferromagnetic layer.

[0001] This application claims priority to prior application JP Appln.No. 2002-127656, the disclosure of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to a laminated ferrimagnetic thinfilm having a magnetization reversion characteristic suitable for a freemagnetic layer of a magneto-resistive effect element or a ferromagnetictunnel junction element, and a magneto-resistive effect element and aferromagnetic tunnel element using this thin film.

[0003] The magneto-resistive effect is a phenomenon that an electricresistance varies based on an external magnetic field. Amagneto-resistive effect element senses a magnitude of the externalmagnetic field applied to the element as a change in an elementresistance value, or has a function to hold this state as a magnitude ofthe element resistance value. In particular, there are many expectationsto application of a spin valve type GMR element and a ferromagnetictunnel junction element each having a large magneto-resistive changeratio (MR ratio) in a low external magnetic field area at a roomtemperature to a high recording density compatible reproduction magnetichead and a high density solid-state magnetic memory (MRAM).

[0004] These magneto-resistive effect elements consist of a freemagnetic layer capable of setting a magnetization direction free withrespect to the external magnetic field, a pinned magnetic layerincluding a mechanism to fix a magnetization direction to the externalmagnetic field, and a non-magnetic layer which is arranged between andcomes into contact with these layers.

[0005] The magneto-resistive effect occurs when a resistance of theelement varies due to a relative magnetization angle of the magneticlayers on the both sides with the non-magnetic layer sandwichedtherebetween. Substantially eliminating the magnetic coupling betweenthe free magnetic layer and the pinned magnetic layer realizes aso-called spin valve type element operation that only a magnetizationdirection of the free magnetic layer varies with respect to the externalmagnetic field, and obtains the magneto-resistive effect sensitive tothe external magnetic field.

[0006] As magnetic materials (ferromagnetic substances), there arewidely known Co, Ni, Fe and alloys of these materials. In particular, Coor an alloy including Co, especially a CoFe alloy has a feature of largesaturation magnetization, and Ni or an alloy including Ni, especially anNiFe alloy has a feature of a excellent soft magnetic characteristic(low coercive force). As free magnetic layer materials of themagneto-resistive effect element, a magnetically soft (superior in asoft magnetic characteristic) magnetic material like NiFe is suitableand widely used because of the need to quickly perform magnetizationreversion in a small external magnetic field.

[0007] Further, as to a mechanism which fixes a magnetization directionof the pinned magnetic layer to an external magnetic field, there areemployed a method (coercive force difference type) which uses a magneticmaterial which is magnetically hard as a material and makes itsreverting coercive force larger than that of the free magnetic layer,and a method (exchange biased type) which further positively fixes themagnetization direction to one direction by bringing ananti-ferromagnetic layer into contact with a pinned magnetic layer.

[0008] The element which uses a non-magnetic conductor such as Cu, Agand Au as a non-magnetic layer is a spin valve type GMR elementtypically disclosed in U.S. Pat. No. 5,159,513, and an element whichuses a non-magnetic insulator such as an Al oxide or an Al nitride as anon-magnetic layer is a ferromagnetic tunnel junction element typicallydisclosed in U.S. Pat. No. 5,650,958. A higher MR ratio can be obtainedin the latter element rather than the former element. Furthermore, theboth elements has a difference in direction along which an electriccurrent is passed. Since the in-plane high integration of the element isimportant for an application to a high density solid-state magneticmemory (MRAM), the ferromagnetic tunnel junction element which has ahigher MR ratio and performs energization in a direction vertical to theplane is more preferable.

[0009] On the other hand, as one of thin film structures which can beapplied to the ferromagnetic layer (the free magnetic layer or thepinned magnetic layer) in these magneto-resistive effect elements, thereis a multi-layer magnetic film which is called a laminated ferrimagneticthin film. As apparent from the basic structure disclosed in U.S. Pat.No. 5,341,118, this is a multi-layer thin film consisting of at leasttwo ferromagnetic layers and a non-magnetic intermediate layer which isarranged between and in contact with the ferromagnetic layers. When anon-magnetic transition metal which is preferable as a non-magneticintermediate layer material is used, the extremely stronganti-ferromagnetic interaction (exchange bonding) acts on the bothferromagnetic layers through the non-magnetic intermediate layer, andtheir magnetization directions are always anti-parallel in a lowmagnetic field. Therefore, the magnetic moments of the respectiveferromagnetic layers constituting the laminated ferrimagnetic thin filmare always canceled out, and it is possible to realize an artificialferrimagnetic state having a small magnetic moment corresponding to adifference in film thickness between the respective ferromagneticlayers. In the laminated ferrimagnetic thin film, the magnetic filmthickness can be effectively greatly reduced without extremelydecreasing the film thickness of each ferromagnetic layer.

[0010] The magnitude of the anti-ferromagnetic exchange bonding betweenthe ferromagnetic layers in the laminated ferrimagnetic thin filmdepends on a material and a film thickness of the non-magneticintermediate layer. Physical Review Letters, Vol. 67, p. 3598 (1991)describes that the intensity of the anti-ferromagnetic exchange bondingbetween the ferromagnetic layers in the laminated ferrimagnetic thinfilm depends on a non-magnetic intermediate layer material and theperiodic vibrations are demonstrated with respect to a film thickness ofthe non-magnetic intermediate layer material. It also mentions that, inthe laminated ferrimagnetic thin film which has a simple sandwichstructure that the number of times of repetition=1 and in which filmthicknesses of the respective ferromagnetic layers are equal to eachother, assuming that H_(S) is a saturation magnetic field, M_(S) issaturation magnetization of the ferromagnetic layer to be used and t isa film thickness of the ferromagnetic layer, the bonding intensity (J:anti-ferromagnetic exchange bonding energy) can be obtained based onJ=H_(S)×M_(S)×t/2. In this report, there is described the relationshipbetween the anti-ferromagnetic exchange bonding intensity and manynon-magnetic intermediate layer materials when Co is used as theferromagnetic layer, as well as the tendency that the magnitude of theferromagnetic exchange bonding energy increases in the order of a 5dgroup transition metal, a 4d group transition metal and a 3d grouptransition metal as the non-magnetic intermediate layer material andthat it also increases as a quantity of outermost shell d electronsbecomes larger in the same cycle. Among others, Ru, Rh, Ir and Cu havethe anti-ferromagnetic exchange bonding energy of up to 10⁻³ J/m² (1erg/cm²), which is considerably larger than that of any other element.It is to be noted that, according to Journal of Magnetism and MagneticMaterials, Vol. 165, p. 524 (1997), assuming that t₁ and t₂ are therespective ferromagnetic layer film thicknesses, the anti-ferromagneticexchange bonding energy when the respective ferromagnetic layers havedifferent film thicknesses can be given by J=H_(S)×MS×t₁×t₂/(t₁+t₂).

[0011] It is known that the exchange bonding intensity of the laminatedferrimagnetic layer also depends on a material for the ferromagneticlayer to be used. Physical Review B, Vol. 56, p. 7819 (1997) mentionsthat the anti-ferromagnetic exchange bonding energy when Cu is used asthe non-magnetic intermediate layer and NiFe is used as theferromagnetic layer is not more than J=6×10⁻⁵ J/m² (0.06 erg/cm²), butthis value is far smaller than that obtained when Co is used as theferromagnetic layer. Further, Journal of Applied Physics, Vol. 73, p.5986 (1993) mentions that the exchange bonding intensity becomes smallerwhen NiFe (perm alloy) is used as the ferromagnetic layer rather thanCo, and points out the possibility of the influence of the fact that thesaturation magnetization of NiFe is smaller than that of Co. Japanesepatent application laid-open No. 143223/2001 discloses a film thicknessrange of the non-magnetic intermediate layers (Ru, Cr, Ir and Rh) bywhich the magnitude of a saturation magnetic field to be obtained ispreferable when NiFe and Co are used as the ferromagnetic layer materialin the laminated ferrimagnetic thin film. By using the relationshipbetween the saturation magnetic field disclosed herein and thenon-magnetic intermediate layer film thickness, the relationship betweenthe saturation magnetization of each ferromagnetic layer material andits film thickness, and a relational expression of theanti-ferromagnetic exchange bonding energy J and the saturation magneticfield H_(S) mentioned above (J=H_(S)×M_(S)×t₁×t₂/(t₁+t₂)), thenon-magnetic intermediate layer film thickness dependence of eachanti-ferromagnetic exchange bonding intensity when the ferromagneticlayer materials are NiFe and Co can be obtained.

[0012]FIGS. 1 and 2 are graphs showing the relationship between theanti-ferromagnetic exchange bonding energy of NiFe and Co obtained bythe above method and film thicknesses of the non-magnetic intermediatelayers (Ru, Rh, Ir).

[0013] Description will now be given as to a prior art concerning theapplication of the laminated ferrimagnetic thin film to themagneto-resistive effect element. The magneto-resistive effect elementhaving a laminated ferri type pinned magnetic layer will be firstexplained. In the magneto-resistive effect element, as described above,in order to subject the free magnetic layer to magnetization reversionin accordance with a change in an external magnetic field (in order tocause the magneto-resistive effect element to operate in the spin valvemanner), the magnetic effect acting between the free magnetic layer andthe pinned magnetic layer must be reduced to substantially zero. Whenthe laminated ferrimagnetic thin film is applied to the pinned magneticlayer, however, the influence of the pinned magnetic layer onmagnetization reversion of the free magnetic layer can be furtherreduced. The basic structure of the magneto-resistive effect elementhaving the laminated ferri type pinned magnetic layer is disclosed inU.S. Pat. No. 5,465,185. Usually, in the magneto-resistive effectelement, the phenomenon that a fixed amount of the reverting magneticfield of the free magnetic layer is shifted can be observed due to theinfluence of the static magnetic field formed by the magnetic charge ofan end of the pinned magnetic layer. In the magneto-resistive effectelement having the laminated ferri type pinned magnetic layer, however,the static magnetic field formed by the pinned magnetic layer can beminimized by the magnetic thin film reducing effect of the pinnedmagnetic layer, thereby reducing the shift of the reverting magneticfield of the free magnetic layer. In the magneto-resistive effectelement having the laminated ferri type pinned magnetic layer, animprovement to make the pinned magnetic layer more preferable (themagnetic effect of the pinned magnetic layer acting on the free magneticlayer is further reduced) has been advanced. For example, Japanesepatent application laid-open No. 052317/2001 discloses a method by whichgrain growth is suppressed due to the buffer effect by realizing thethree-layer structure with an appropriate material and film thickness ofa ferromagnetic layer on a free magnetic layer side of two ferromagneticlayers constituting a laminated ferri type pinned magnetic layer,thereby smoothing the top face of the pinned magnetic layer on the freemagnetic layer side. As a result, the direct ferromagnetic coupling(which is generally called nail coupling) due to roughness actingbetween the pinned magnetic layer and the free magnetic layer can bereduced. In such a laminated ferri type pinned magnetic layer, it isknow that there is also an advantage to make the pinned magnetic layermagnetically more hard as well as the above-described advantages. Thatis, in the magneto-resistive effect element having the laminated ferritype pinned magnetic layer, since the pinned magnetic layer is hard tobe reverted with respect to the external magnetic field, it is furtherpreferable as the pinned magnetic layer whose magnetization directionmust be fixed. Journal of Applied Physics, Vol. 85, p. 5276 reports thecoercive force difference type ferromagnetic tunnel junction.

[0014] The magneto-resistive effect element having the laminatedferrimagnetic layer will now be described. Its basic structure isdisclosed in U.S. Pat. No. 5,408,377. The advantage of using thelaminated ferrimagnetic thin film for the free magnetic layer lies inthat reducing an effective magnetic film thickness of the free magneticlayer can decrease the magnitude of a demagnetizing field formed by thefree magnetic layer itself which is in proportion to the magnetic filmthickness. The reverting magnetic field of the micro-fabricated freemagnetic layer is increased in inverse proportion to an element size dueto the effect of the demagnetizing field, but the magneto-resistiveeffect element using the laminated ferri type free magnetic layer canreduce the reverting magnetic field. As a result, in a magnetic head,the magnetic field sensitivity of a fine element can be improved. Also,in a solid-state magnetic memory, the switching magnetic field of thefine element can be reduced, thereby enabling power saving.

[0015] Thus, realizing minuteness of an element size is required withrespect to a demand for the high recording density of a reproductionmagnetic head and a demand for the high integration of a solid-statemagnetic memory, and it is expected that suppression of an increase inthe reverting magnetic field of the free magnetic layer caused due tothe above-described realization of minuteness becomes very important infuture. As different from the pinned magnetic layer, however, there isalmost no improvement report about the magneto-resistive effect elementin which the laminated ferrimagnetic thin film is applied with respectto the free magnetic layer.

[0016] However, in the prior art laminated ferrimagnetic thin film, thelarge anti-ferromagnetic exchange bonding energy can be readily obtainedwhen Co or CoFe is used as a ferromagnetic layer material, but it isdifficult to produce the large anti-ferromagnetic exchange bondingenergy by using Ni or NiFe. Referring to FIG. 2, when Co is used as aferromagnetic layer material, the large anti-ferromagnetic exchangebonding energy can be obtained in a large non-magnetic intermediatelayer thin film range of approximately 0.6 nm if the non-magneticintermediate layer is formed of Ru, Ir or Rh. However, referring to FIG.1, the non-magnetic intermediate layer film thickness range in which thelarge anti-ferromagnetic exchange bonding energy of not less than, e.g.,10⁻³ J/m² (1 erg/cm²) when NiFe is used does not exist if thenon-magnetic intermediate layer is formed of Ru or Ir. Further, in caseof Rh, this range is not more than 0.1 nm, which is very narrow. Namely,when Ni or NiFe is used as a ferromagnetic layer material, very precisecontrol over the non-magnetic intermediate layer film thickness isrequired as compared with the case that Co or CoFe is used. Whenapplying to a device, irregularities in film thickness between lots orin a wafer must be taken into consideration, which results in a seriousproblem. As the laminated ferrimagnetic thin film suitable for the freemagnetic layer in the magneto-resistive effect element, there isrequired the laminated ferrimagnetic thin film which can simultaneouslyrealize the large anti-ferromagnetic exchange bonding energy and theexcellent soft magnetic characteristic equivalent to that of Ni or NiFeand does not require precise control of the non-magnetic intermediatelayer film thickness.

SUMMARY OF THE INVENTION

[0017] It is therefore an object of the present invention to provide alaminated ferrimagnetic thin film which can simultaneously realize thelarge anti-ferromagnetic exchange bonding energy and the excellent softmagnetic characteristic and does not require precise control of anon-magnetic intermediate layer film thickness.

[0018] It is another object of the present invention to provide amagneto-resistive effect element and a ferromagnetic tunnel junctionelement which have steep magnetization reversion of a free magneticlayer and a low coercive force, and can be readily manufactured.

[0019] A laminated ferrimagnetic thin film according to the presentinvention consists of a first ferromagnetic layer, a secondferromagnetic layer and a non-magnetic intermediate layer which isarranged between these layers and in contact with them, the firstferromagnetic layer and the second ferromagnetic layer beingmagnetically coupled through the non-magnetic intermediate layer in theanti-ferromagnetic manner.

[0020] According to a first aspect of the present invention, there isprovided a laminated ferrimagnetic thin film comprising: a first mainferromagnetic layer in which the first ferromagnetic layer consists ofat least one layer; and a first interface ferromagnetic layer which isarranged between the first main ferromagnetic layer and the non-magneticintermediate layer and in contact with them. Further, it also comprisesa second main ferromagnetic layer in which the second ferromagneticlayer consists of at least one layer, and a second interfaceferromagnetic layer which is arranged between the second mainferromagnetic layer and the non-magnetic intermediate layer and incontact with them. Each of the first interface ferromagnetic layer andthe second interface ferromagnetic layer is formed of Co or an alloyincluding Co. Each of at least one layer in the first main ferromagneticlayer and at least one layer in the second main ferromagnetic layer isformed of a soft magnetic film, and a total film thickness of layersconsisting of soft magnetic layers in the first main ferromagnetic layeris not less than 60% of a film thickness of the first ferromagneticlayer, and a total film thickness of layers consisting of soft magneticlayers in the second main ferromagnetic layer is not less than 60% of afilm thickness of the second ferromagnetic layer.

[0021] According to a second aspect of the present invention, there isprovided a laminated ferrimagnetic thin film, wherein the firstferromagnetic layer consists of two layers, i.e., a first mainferromagnetic layer and a first interface ferromagnetic layer which isarranged between the first main ferromagnetic layer and the non-magneticintermediate layer and in contact with them. The second ferromagneticlayer consists of two layers, i.e., a second main ferromagnetic layerand a second interface ferromagnetic layer which is arranged between thesecond main ferromagnetic layer and the non-magnetic intermediate layerand in contact with them. Each of the first interface ferromagneticlayer and the second interface ferromagnetic layer is formed of Co or analloy including Co. Each of the first main ferromagnetic layer and thesecond main ferromagnetic layer is formed by a soft magnetic film. Afilm thickness of the first main ferromagnetic layer is not less than60% of a film thickness of the first ferromagnetic layer, and a filmthickness of the second main ferromagnetic layer is not less than 60% ofa film thickness of the second ferromagnetic layer.

[0022] In such a laminated ferrimagnetic thin film, e.g., thenon-magnetic intermediate layer is formed of one type of metal selectedfrom a group including Ru, Rh, Ir and Cu, or an alloy having as a maincomponent one type selected from a group including Ru, Rh, Ir and Cu.

[0023] Furthermore, the alloy including Co is, e.g., a Co—Fe alloy or aCo_(x)Fe_(1−x) (0.75≦X<1) alloy. Moreover, the soft magnetic film is,e.g., Ni or an alloy including Ni. In this case, the soft magnetic filmis formed of, e.g., an Ni—Fe alloy or an Ni_(x)Fe_(1−x) (0.35≦X<1)alloy.

[0024] On the other hand, according to the present invention, there isprovided a magneto-resistive effect element comprising: a free magneticlayer which can freely change a magnetization direction with respect toan external magnetic field; a pinned magnetic layer including amechanism to fix its magnetization direction with respect to theexternal magnetic field; and a non-magnetic layer which is arrangedbetween the free magnetic layer and the pinned magnetic layer and incontact with them, an element resistance being changed by application ofthe external magnetic field, wherein the free magnetic layer is thelaminated ferrimagnetic thin film.

[0025] In addition, according to the present invention, there isprovided a ferromagnetic tunnel junction element comprising: a freemagnetic layer which can freely change its magnetization direction withrespect to an external magnetic field; a pinned magnetic layer includinga mechanism which fixes its magnetization direction with respect to theexternal magnetic field; and a non-magnetic insulating layer which isarranged between the free magnetic layer and the pinned magnetic layerand in contact with them, an element resistance being changed byapplication of the external magnetic field, wherein the free magneticlayer is a laminated ferrimagnetic thin film according to any of claims1 to 8.

[0026] The present inventors revealed that it is necessary tosimultaneously realize that an anti-ferromagnetic exchange bondingenergy between the two ferromagnetic layers constituting the syntheticferri type free magnetic layer is large and that the entireferromagnetic layer is formed of a material superior in a soft magneticcharacteristic which is equivalent to Ni or an alloy including Ni (e.g.,NiFe) in order to obtain a small reverting coercive force suitable forthe laminated ferri type free magnetic layer in the magneto-resistiveeffect element through various examinations and experiments on thelaminated ferrimagnetic thin film having the magnetization reversioncharacteristic suitable for the laminated ferri type free magnetic layerin the magneto-resistive effect element.

[0027] Specifically, the present inventors paid attention to astructure, a material and a film thickness of the ferromagnetic layer inthe laminated ferrimagnetic thin film and conducted various kinds ofexperiments. As a result, they discovered that it is possible to readilyobtain the laminated ferrimagnetic thin film (without performing precisenon-magnetic intermediate layer film thickness control) which canrealize both the large anti-ferromagnetic exchange bonding energy andthe excellent soft magnetic characteristic by using a material of thenon-magnetic intermediate layer and a structure, a material and a filmthickness of the ferromagnetic layer described in appended claims,thereby bringing the present invention to completion.

[0028] The laminated ferrimagnetic thin film according to the presentinvention can simultaneously realize both the anti-ferromagneticexchange coupling between the ferromagnetic layers having stiffnessequivalent to a Co/Ru/Co-based material and a large margin relative tothe non-magnetic intermediate layer film thickness, and the excellentsoft magnetic characteristic equivalent to that of an Ni-based magneticmaterial.

[0029] Therefore, according to the present invention, it is possible toreadily obtain the laminated ferrimagnetic thin film which has amagnetic characteristic (rapid magnetization reversion with a smallcoercive force) suitable for the free magnetic layer in themagneto-resistive effect element (without performing precisenon-magnetic intermediate layer film thickness control).

[0030] Additionally, since the magneto-resistive effect element and theferromagnetic tunnel junction element according to the present inventionare characterized in use of the laminated ferrimagnetic thin film of thepresent invention for the free magnetic layer, the preferable magneticcharacteristic (the magnetization reversion of the free magnetic layeris rapid and has a low coercive force) can be readily obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031]FIG. 1 is a view showing a relationship between ananti-ferromagnetic exchange bonding energy and a non-magneticintermediate layer film thickness of a prior art laminated ferrimagneticthin film using NiFe for a ferromagnetic layer;

[0032]FIG. 2 is a view showing a relationship between ananti-ferromagnetic exchange bonding energy and a non-magneticintermediate layer film thickness of a prior art laminated ferrimagneticthin film using Co for a ferromagnetic layer;

[0033]FIG. 3 is a cross-sectional view showing a basic film structure ofa laminated ferrimagnetic thin film according to a first embodiment;

[0034]FIG. 4 is a cross-sectional view showing a basic film structure ofa laminated ferrimagnetic thin film according to a second embodiment;

[0035]FIG. 5 is a cross-sectional view showing a basic film structure ofa magneto-resistive effect element according to a third embodiment;

[0036]FIG. 6 is a cross-sectional view showing a basic film structure ofa magneto-resistive effect element according to a fourth embodiment;

[0037]FIG. 7 is a cross-sectional view showing a basic film structure ofthe laminated ferrimagnetic thin film according to the first example;

[0038]FIG. 8 is a view showing a relationship between an externalmagnetic field and a magnetic moment per unit film area in the laminatedferrimagnetic thin film according to the first example;

[0039]FIG. 9 is a cross-sectional view showing a basic film structure ofa laminated ferrimagnetic thin film according to a first comparativeexample;

[0040]FIG. 10 is a view showing a relationship between an externalmagnetic field and a magnetic moment per unit film area in the laminatedferrimagnetic thin film according to the first comparative example;

[0041]FIG. 11 is a view showing a relationship between ananti-ferromagnetic exchange bonding energy and an interfaceferromagnetic layer (CoFe) film thickness in the laminated ferrimagneticthi; film according to the second example;

[0042]FIG. 12 is a cross-sectional view showing a basic film structureof a laminated ferrimagnetic thin film according to the third example;

[0043]FIG. 13 is a view showing a relationship between an externalmagnetic field and a magnetic moment per unit film area in the laminatedferrimagnetic thin film according to the third example;

[0044]FIG. 14 is a cross-sectional view showing a basic film structureof a laminated ferrimagnetic thin film according to a second comparativeexample;

[0045]FIG. 15 is a view showing a relationship between an externalmagnetic field and a magnetic moment per unit film area in the laminatedferrimagnetic thin film according to the second comparative example;

[0046]FIG. 16 is a view showing a relationship between a differencemagnetization reversion coercive force (H_(C)) and a percentage (%) of amain ferromagnetic layer (NiFe) film thickness in each ferromagneticlayer in a laminated ferrimagnetic thin film according to a fourthexample;

[0047]FIG. 17 is a cross-sectional view showing a basic film structureof a laminated ferrimagnetic thin film according to a fifth example;

[0048]FIG. 18 is a cross-sectional view showing a basic film structureof a ferromagnetic tunnel junction element according to a sixth example;

[0049]FIGS. 19A through 19G are views showing a element shapemanufacturing process of a ferromagnetic tunnel junction elementaccording to the sixth embodiment and a seventh example; and

[0050]FIG. 20 is a cross-sectional view showing a basic film thicknessof the ferromagnetic tunnel junction element according to the seventhexample.

DESCRIPTION OF THE PREFERRED EMBODIMENTS:

[0051] Preferred embodiments according to the present invention will nowbe concretely described hereinafter with reference to the accompanyingdrawings.

[0052] (First Embodiment)

[0053] Referring to FIG. 3, a buffer layer 301 is formed on a substrate300, and on the buffer layer 301 are superimposed a first mainferromagnetic layer 302, a first interface ferromagnetic layer 303, anon-magnetic intermediate layer 304, a second interface ferromagneticlayer 305, a second main ferromagnetic layer 306 and a cap layer 307 inthe mentioned order.

[0054] A material constituting the non-magnetic intermediate layer isany non-magnetic transition metal of Ru, Rh, Ir and Cu, or an alloyhaving as a main component any of these elements.

[0055] A material of each of the first interface ferromagnetic layer 303and the second interface ferromagnetic layer 305 is Co or an alloyincluding Co. As an alloy including Co, Co—Fe, Co—Cr, Co—Cu, Co—Pt,Co—Mn and others are preferable. Among others, Co—Fe is most preferable.Further, its composition is determined as Co_(x)Fe_(1−x) (0.75≦X<1), andit is more preferable to set a Co composition X to 75 atom % or above.

[0056] A film thickness of each of the first interface ferromagneticlayer 303 and the second interface ferromagnetic layer 305 is at leastnot less than 0.1 nm.

[0057] A material of each of the first main ferromagnetic layer 302 andthe second main ferromagnetic layer 306 is a soft magnetic film of Ni oran Ni alloy. Specifically, as a soft magnetic film of an Ni alloy, thereare Ni—Fe, Ni—Fe—Mo, Ni—Fe—Nb, Ni—Fe—B, Ni—Fe—Cr—Cu, Ni—Fe—Co, Ni—Co andothers. Above all, Ni—Fe is particularly superior in the soft magnetismand thus preferable. Furthermore, if a perm alloy (Ni_(x)Fe_(1−x)(0.35≦X<1)) is used and an Ni composition X is determined as 35 atom %or above, the coercive force can be reduced to 79 A/m (1(0e)) or below.This soft magnetic film has a smaller coercive force than that of Co ora Co alloy constituting the first and second interface ferromagneticlayers 303 and 305 and has the excellent soft magnetic characteristic.

[0058] In this embodiment, each of the first main ferromagnetic layer302 and the second main ferromagnetic layer 306 is a single layer, andits overall thickness is formed by a soft magnetic film. Therefore, afilm thickness of the first main ferromagnetic layer 302 is not lessthan 60% of a film thickness of the first ferromagnetic layer 308, and afilm thickness of the second main ferromagnetic layer 306 is not lessthan 60% of a film thickness of the second ferromagnetic layer 309.However, an upper limit value of the film thickness of the first mainferromagnetic layer 302 or the second main ferromagnetic layer 306 isobtained by subtracting a thickness of the first interface ferromagneticlayer 303 or the second interface ferromagnetic layer 305 from the firstferromagnetic layer 308 or the second ferromagnetic layer 309,respectively.

[0059] Ta, Zr, Ti or the like is used for the buffer layer 301. However,any other material can be used as long as it has a function to enhancethe contact between the first main ferromagnetic layer 302 and thesubstrate 300. Moreover, the buffer layer 301 may not be formed in somecases.

[0060] Ta, Zr, Ti, Al or the like is used for the cap layer 307.However, any other material can be used as long as it can prevent thesurface of the second main ferromagnetic layer 306 from beingdeteriorated due to exposure to the air. In addition, the cap layer 307may not be formed in some cases.

[0061] The first main ferromagnetic layer 302 and the first interfaceferromagnetic layer 303 constitute the first ferromagnetic layer 308,and the second main ferromagnetic layer 306 and the second interfaceferromagnetic layer 305 constitute the second ferromagnetic layer 309.The first ferromagnetic layer 308 and the second ferromagnetic layer 309are magnetically coupled in such a manner that directions of theirmagnetic moments become anti-parallel to each other by theanti-ferromagnetic exchange bonding effect through the non-magneticintermediate layer 304.

[0062] An operation of the magnetic laminated ferrimagnetic thin filmhaving the above-described structure will now be described. When thelaminated ferrimagnetic thin film according to this embodiment is usedas a free magnetic layer in, e.g., a magneto-resistive effect element ora ferromagnetic tunnel element, a first interface ferromagnetic layer604 and a second interface ferromagnetic layer 606 each of whichconsists of Co or a Co alloy are superimposed with a non-magneticintermediate layer 605 therebetween, thereby obtaining the veryexcellent coupling characteristic. Furthermore, since the firstferromagnetic layer 308 and the second ferromagnetic layer 309 areformed by a first main ferromagnetic layer 302 and a second mainferromagnetic layer 306 consisting of Ni or an Ni alloy that 60% or moreof their film thickness is a soft magnetic film, the entireferromagnetic layer can acquire the soft magnetic characteristicequivalent to that obtained when the conventional ferromagnetic layerconsisting of an NiFe alloy or the like is used.

[0063] Since each of the first interface ferromagnetic layer 303 and thesecond interface ferromagnetic layer 305 is formed of Co or an Co alloy,as shown in FIG. 2, the anti-ferromagnetic exchange bonding energy isincreased in a range that the film thickness of the non-magneticintermediate layer 304 is large, and a selection range of a thickness ofthe non-magnetic intermediate layer where the anti-ferromagneticexchange bonding energy of not less than 10⁻³ J/m² (1 erg/cm²) can beobtained is wide. Therefore, there is no problem if the accuracy of thethickness is low when forming the non-magnetic intermediate layer. It isto be noted that, when the ferromagnetic layer consists of an NiFealloy, the anti-ferromagnetic exchange bonding energy is low as shown inFIG. 1, and a range of the thickness with which the bonding energy of10⁻³ J/m² (1 erg/cm²) can be obtained is approximately 0.47 to 0.6 nmand very narrow even if Rh is used as the non-magnetic intermediatelayer. Therefore, in order to obtain the bonding energy of this level,the thickness of the non-magnetic intermediate layer must be accuratelyformed so as to fall within the above-described range. Accordingly, themagnetic laminated ferrimagnetic thin film according to this embodimentcan be readily manufactured, and it is possible to easily produce themagnetic laminated ferrimagnetic thin film with the high performance.Moreover, in this embodiment, since the ferromagnetic layer is atwo-layer superimposed body including the interface ferromagnetic layerconsisting of Co or a Co alloy and the main ferromagnetic layer 302 or306 consisting of Ni or an Ni alloy which has a smaller coercive forcethan that of Co or a Co alloy and is a soft magnetic film superior inthe soft magnetic film, the soft magnetic characteristic is excellent,and the memory effect of the magnetic spin as a free magnetic layer isalso good.

[0064] It is to be noted that the above-described magnetic laminatedferrimagnetic thin film can be combined with a pinned magnetic layer aswill be described later and used as a free magnetic layer in amagneto-resistive effect element or a ferromagnetic tunnel element. Inaddition, when the magnetic laminated ferrimagnetic thin film is formedof a material and with a film thickness shown in FIG. 7, it has acharacteristic illustrated in FIG. 8 as will be described later.Therefore, this magnetic laminated ferrimagnetic thin film can be solelyused as, e.g., a magnetic shield.

[0065] (Second Embodiment)

[0066] A second embodiment according to the present invention will nowbe described. Although this laminated ferrimagnetic thin film basicallyhas the same structure as the laminated ferrimagnetic thin film shown inFIG. 3, the laminated ferrimagnetic thin film according to the secondembodiment is different from the laminated ferrimagnetic thin filmaccording to the first embodiment shown in FIG. 3 in that either or bothof the first main ferromagnetic layer and the second main ferromagneticlayer are constituted by a plurality of layers, i.e., two or morelayers. However, in the example depicted in FIG. 4, each of the firstmain ferromagnetic layer and the second main ferromagnetic layerconsists of the two magnetic layers. Referring to FIG. 4, the laminatedferrimagnetic thin film according to the second embodiment will now bedescribed.

[0067] As shown in FIG. 4, in the laminated ferrimagnetic thin filmaccording to this embodiment, a buffer layer 601 is formed on asubstrate 600, and on this buffer layer 601 are superimposed a firstferromagnetic layer 602, a second ferromagnetic layer 603, a firstinterface ferromagnetic layer 604, a non-magnetic intermediate layer605, a second interface ferromagnetic layer 606, a third ferromagneticlayer 607, a fourth ferromagnetic layer 608 and a cap layer 609 in thementioned order.

[0068] The non-magnetic intermediate layer 605 is formed of anynon-magnetic transition metal of Ru, Rh, Ir and Cu, or an alloy havingas a main component this non-magnetic transition metal.

[0069] A material of each of the first interface ferromagnetic layer 604and the second interface ferromagnetic layer 606 is Co or an alloyincluding Co. As an alloy including Co, materials such as Co—Fe, Co—Cr,Co—Cu, Co—Pt, Co—Mn and the like are preferable. Above all, a Co—Fealloy is most preferable. Further, if its composition is Co_(x)Fe_(1−x)(0.75≦X<1) and a Co composition X is not less than 75 atom %, it becomesmore preferable.

[0070] A film thickness of each of the first interface ferromagneticlayer 604 and the second interface ferromagnetic layer 606 is at leastnot less than 0.1 nm.

[0071] It is determined that a material of at least one of the firstferromagnetic layer 602 and the second ferromagnetic layer 603 is Ni oran alloy including Ni. Furthermore, it is determined that a material ofat least one of the third ferromagnetic layer 607 and the fourthferromagnetic layer 604 is Ni or an alloy including Ni. As Ni or analloy including Ni, a soft magnetic film including Ni as a component ispreferable. Specifically, as a soft magnetic film including Ni as acomponent, there are Ni—Fe, Ni—Fe—Mo, Ni—Fe—Nb, Ni—Fe—B, Ni—Fe—Cr—Cu,Ni—Fe—Co, Ni—Co, Ni—Fe—Co and the like. Above all, an Ni—Fe alloy isparticularly superior in the soft magnetism and most preferable.Furthermore, if it is a perm alloy (Ni_(x)Fe_(1−x) (0.35≦X<1)) and an Nicomposition X is not less than 35 atom %, the coercive force can bereduced to 79 A/m (1(0e)) or below.

[0072] A total film thickness of layers formed of Ni or an alloyincluding Ni in the first ferromagnetic layer 602 and the secondferromagnetic layer 603 is determined to be not less than 60% of a filmthickness of the first ferromagnetic layer 612. Moreover, a total filmthickness of layers formed of Ni or an alloy including Ni in the thirdferromagnetic layer 607 and the fourth ferromagnetic layer 608 isdetermined to be not less than 60% of a film thickness of the secondferromagnetic layer 613.

[0073] The buffer layer 601 can be formed of Ta, Zr, Ti and the like.However, the buffer layer 601 can be formed by using any other materialas long as it can improve the contact between the first ferromagneticlayer 602 and the substrate 600. In addition, the buffer layer 601 maynot be formed in some cases.

[0074] The cap layer 609 can be formed of Ta, Zr, Ti, Al and others.However, any other material can be used for the cap layer 609 as long asit can prevent the surface of the fourth ferromagnetic layer 608 frombeing deteriorated due to exposure to air, and the cap layer 609 may notbe formed in some cases.

[0075] The first ferromagnetic layer 602 and the second ferromagneticlayer 603 constitute the first main ferromagnetic layer 610, and thethird ferromagnetic layer 607 and the fourth ferromagnetic layer 608constitute the second main ferromagnetic layer 611. In addition, thefirst main ferromagnetic layer 610 and the first interface ferromagneticlayer 604 constitute the first ferromagnetic layer 612, and the secondmain ferromagnetic layer 611 and the second interface ferromagneticlayer 606 constitute the second ferromagnetic layer 613. The firstferromagnetic layer 612 and the second ferromagnetic layer 613 aremagnetically coupled in such a manner that directions of their magneticmoments become anti-parallel to each other by the anti-ferromagneticexchange bonding effect through the non-magnetic intermediate layer 605.

[0076] Although the above has described an example of the secondembodiment when each of the first main ferromagnetic layer and thesecond main ferromagnetic layer consists of two magnetic layers, one ofthe first main ferromagnetic layer and the second main ferromagneticlayer may have the same one-layer structure as the first embodiment.Further, if at least one layer in the first main ferromagnetic layer isformed of Ni or an alloy including Ni and a total film thickness oflayers formed of Ni or an alloy including Ni in the first mainferromagnetic layer is not less than 60% of a film thickness of thefirst ferromagnetic layer, the first main ferromagnetic layer may have astructure constituted by three or more magnetic layers. Likewise, if atleast one layer in the second main ferromagnetic layer is formed of Nior an alloy including Ni and a total film thickness of layers formed ofNi or an alloy including Ni in the second main ferromagnetic layer isnot less than 60% of a film thickness of the second ferromagnetic layer,the second main ferromagnetic layer may have a structure constituted bythree or more magnetic layers. Furthermore, the upper limit of thenumber of layers in the first main ferromagnetic layer or the secondferromagnetic layer is not particularly restricted, and a layer having acomponent concentration of its material being inclined in a layerthickness direction may be included.

[0077] It is to be noted that a material of layers other than layersformed of Ni or an alloy including Ni in the first main ferromagneticlayer or the second main ferromagnetic layer is not particularly limitedas long as it is a magnetic material. It is, however, desirable thatthis layer is formed of a material having any other effect.

[0078] (Third Embodiment)

[0079] Description will now be given as to a structure and amanufacturing method of a magneto-resistive effect element according toa third embodiment of the present invention. The magneto-resistiveeffect element according to this embodiment is a magneto-resistiveeffect element in which the laminated ferrimagnetic thin film is used asa free magnetic layer thereof.

[0080] In the magneto-resistive effect element according to the thirdembodiment of the present invention, as shown in FIG. 5, a first bufferlayer 401 is formed on a substrate 400, an underlying electrode layer402 is formed on the first buffer layer 401, and on the underlyingelectrode layer 402 are formed a second buffer layer 403, a pinnedmagnetic layer 404, a non-magnetic layer 405, a first main ferromagneticlayer 406, a first interface ferromagnetic layer 407, a non-magneticintermediate layer 408, a second interface ferromagnetic layer 409, asecond main ferromagnetic layer 410 and a cap layer 411 in the mentionedorder.

[0081] It is determined that a material of the non-magnetic intermediatelayer 408 is any one of Ru, Rh, Ir and Cu, or a non-magnetic transitionmetal having any of these materials as a main component.

[0082] It is determined that a material of each of the first interfaceferromagnetic layer 407 and the second interface ferromagnetic layer 409is Co or a Co alloy. As a Co alloy, Co—Fe, Co—Cr, Co—Cu, Co—Pt, Co—Mnand the like are preferable. Above all, Co—Fe is most preferable.Furthermore, if its composition is Co_(x)Fe_(1−x) (0.75≦X<1) and a Cocomposition X is not less than 75 atom %, it becomes more preferable.

[0083] It is determined that a film thickness of each of the firstinterface ferromagnetic layer 407 and the second interface ferromagneticlayer 409 is at least 0.1 nm or above.

[0084] Each of the first main ferromagnetic layer 406 and the secondmain ferromagnetic layer 410 can be formed of Ni or an Ni alloy. As anNi alloy, a soft magnetic film including Ni as a component ispreferable. Specifically, as a soft magnetic film including Ni as acomponent, there are Ni—Fe, Ni—Fe—Mo, Ni—Fe—Nb, Ni—Fe—Nb, Ni—Fe—B,Ni—Fe—Cr—Cu, Ni—Fe—Co, Ni—Co, Ni—Fe—Co and the like. Above all, Ni—Fe isparticularly superior in the soft magnetism, and most preferable.Moreover, if it is a perm alloy (Ni_(x)Fe_(1−x) (0.35≦X<1) and an Nicomposition X is not less than 35 atom %, the coercive force can bereduced to 79 A/m (1(0e)) or below.

[0085] It is determined that a film thickness of the first mainferromagnetic layer 406 is not less than 60% of a film thickness of thefirst free magnetic layer 412, and a film thickness of the second mainferromagnetic layer 410 is not less than 60% of a film thickness of thesecond free magnetic layer 413.

[0086] Each of the first buffer layer 401 and the second buffer layer403 can be formed of Ta, Zr, Ti and the like. However, it is good enoughto use a material having a function of, e.g., improving the contactbetween the underlying electrode layer 402 and the substrate 400 orbetween the pinned magnetic layer 404 and the underlying electrode layer402, and these buffer layers 401 and 403 may not be formed in somecases.

[0087] Ta, Zr, Ti, Al or the like is used for the cap layer 411.However, any other material can be used if the cap layer is at least onelayer having a function of, e.g., preventing the surface of the secondmain ferromagnetic layer 410 from being deteriorated due to exposure toair, and the cap layer 411 may not be formed in some cases.

[0088] The underlying electrode layer 402 can be formed of Al. However,it may be formed by using any other metal material such as Ag, Cu, Au orPt having a small specific resistance, and the underlying electrodelayer 402 may be formed by using any other material or may not be formedin some cases.

[0089] As a material of the pinned magnetic layer 404, Co, CoFe or thelike is preferable. However, any other material can be used as long asit has a magnetic characteristic which hardly causes reversion withrespect to an external magnetic field. Moreover, the pinned magneticlayer 404 can be constituted by a plurality of layers. In particular, alaminated ferri type three-layer structure or a two-layer structureincluding the ferromagnetic layer/anti-ferromagnetic layer is morepreferable since it can positively fix its magnetization direction.

[0090] A non-magnetic good conductor such as Cu, Au or Ag, or anon-magnetic insulator such as an Al oxide, a Ta oxide or an Al nitrideis used for the non-magnetic layer 405. An element which is of a typeusing a non-magnetic good conductor such as Cu, Au, Ag or the like iscalled a spin valve type GMR element, and an element which is of a typeusing a non-magnetic insulator such as an Al oxide, a Ta oxide or an Alnitride is called a ferromagnetic tunnel junction element. In case ofthe ferromagnetic tunnel junction element, it is possible to employ amethod by which a film of a non-magnetic metal layer formed of, e.g., Alis formed and its surface is then oxidized or azotized by using a gasincluding oxygen or nitrogen, thereby forming the non-magnetic layer 405as an insulator.

[0091] Description will now be given as to an operation of themagneto-resistive effect element having the above-described structure.The first main ferromagnetic layer 406 and the first interfaceferromagnetic layer 407 constitute the first free magnetic layer 412,and the second main ferromagnetic layer 410 and the second interfaceferromagnetic layer 408 constitute the second free magnetic layer 413.The first free magnetic layer 412 and the second free magnetic layer 413are magnetically coupled in such a manner that directions of theirmagnetic moments become anti-parallel to each other by theanti-ferromagnetic exchange bonding effect through the non-magneticintermediate layer 408, and function as a free magnetic layers. Thefirst free magnetic layer 412, the non-magnetic intermediate layer 408and the second free magnetic layer 413 constitute the free magneticlayer 414. In addition, the pinned magnetic layer 404, the non-magneticlayer 405 and the free magnetic layer 414 constitute a magneto-resistiveeffect portion 415 which varies the resistance due to a change in anexternal magnetic field and demonstrates the magneto-resistive effect.

[0092] In recent years, there have been demanded high integration andminiaturization even in the magneto-resistive effect element because ofa request of high integration of a thin film device. In this case, afilm thickness of each layer must be reduced in order to decrease aplanar shape. However, when reducing the film thickness, there is aproblem of mixing on the atomic level between layers adjacent to eachother in the vertical direction, there is a limit in reduction inthickness of each layer. In the magneto-resistive effect elementaccording to this embodiment, however, since the free magnetic layer 414has a structure that the first free magnetic layer 412 and the secondfree magnetic layer 413 are superimposed with the non-magneticintermediate layer 408 sandwiched therebetween, the magnetic momentsthat the first free magnetic layer 412 and the second free magneticlayer 413 face the opposite directions are formed, thereby canceling outthe magnetic fields. Therefore, the actual film thicknesses are large,but the magnetic film thicknesses are very small. That is, even thoughthe actual film thickness is not reduced, the free magnetic layer servesas a magnetically thin free magnetic layer. Therefore, themagneto-resistive effect element according to this embodiment isadvantageous in high integration.

[0093] Description will now be given as to a method of manufacturing amagneto-resistive effect element according to a third embodiment. First,films of the first buffer layer 401, the underlying electrode layer 402,and the second buffer layer 403 are formed on the substrate 400. Ifirregularities on the upper part of the underlying electrode layer 402are prominent, it is good to perform a surface flattening treatment suchas ion beam irradiation on the film surface. Then, films of the pinnedmagnetic layer 404 and the non-magnetic layer 405 are formed. Further,films of the first main ferromagnetic layer 406, the first interfaceferromagnetic layer 407, the non-magnetic intermediate layer 408, thesecond interface ferromagnetic layer 409, the second main ferromagneticlayer 410 and the cap layer 411 are formed thereon, thereby bringing amulti-layer thin film structure of the magneto-resistive effect elementaccording to the third embodiment to completion.

[0094] It is to be noted that the advantage of the present inventiondoes not correlate with an absolution positional relationship (filmforming order) between the pinned magnetic layer 404 and the freemagnetic layer 414. As to the magneto-resistive effect portion 415, anentirely inverted structure (entirely inverted film forming order) maybe adopted.

[0095] The manufacturing process is effected with respect to theobtained multi-layer thin film as described below, thereby bringing themagneto-resistive effect element according to the third embodiment tocompletion.

[0096] First, an optical exposure or electron ray exposure technique isused, a resist which defines the underlying electrode shape is producedon the obtained multi-layer thin film. Then, an ion milling or chemicaletching technique is used, and all the layers in the obtainedmulti-layer thin film are processed into an object underlying electrodeshape. It is to be noted that, if the magneto-resistive effect elementis a spin valve type GMR element, the underlying electrode layer 402 isnot particularly necessary, and the underlying electrode shapeprocessing step is not particularly required either.

[0097] Then, the optical exposure or electron ray exposure technique isused, a resist which defines an element shape and an element size ismanufactured. Then, the ion milling or chemical etching technique isused, the magneto-resistive effect portion 415 and the cap layer 411 inthe multi-layer film which has processed into the underlying electrodeshape are processed into an object element shape and element size.

[0098] Then, after performing coating using an insulating layer betweenelectrodes, an upper electrode is formed, thereby bringing themagneto-resistive effect element according to the third embodiment tocompletion.

[0099] (Fourth Embodiment)

[0100] A structure and a manufacturing method of a magneto-resistiveeffect element according to the fourth embodiment of the presentinvention will now be described with reference to the accompanyingdrawings. The magneto-resistive effect element according to thisembodiment uses a laminated ferrimagnetic thin film as its free magneticlayer. Although the magneto-resistive effect element according to thefourth embodiment is basically the same as the magneto-resistive effectelement according to the third embodiment, either or both of the firstmain ferromagnetic layer and the second main ferromagnetic layer areconstituted by a plurality of, i.e., two or more layers with respect tothe magneto-resistive effect element according to the third embodiment.

[0101]FIG. 6 is a cross-sectional view showing an element in which eachof the first main ferromagnetic layer and the second main ferromagneticlayer is constituted by two magnetic layers as an example of the fourthembodiment according to the present invention. As shown in FIG. 6, inthe magneto-resistive effect element according to this embodiment, on asubstrate 800 are formed a first buffer layer 801, an underlyingelectrode layer 802, a second buffer layer 803, a pinned magnetic layer804, a non-magnetic layer 805, a first ferromagnetic layer 806, a secondferromagnetic layer 807, a first interface ferromagnetic layer 808, anon-magnetic intermediate layer 809, a second interface ferromagneticlayer 810, a third ferromagnetic layer 811, a fourth ferromagnetic layer812 and a cap layer 813 in the mentioned order.

[0102] The non-magnetic intermediate layer 809 is formed of anynon-magnetic transition metal selected from Ru, Rh, Ir and Cu, or of analloy including this non-magnetic transition metal as a main component.

[0103] A material of each of the first interface ferromagnetic layer 808and the second interface ferromagnetic layer 810 is Co or an alloyincluding Co. As an alloy including Co, Co—Fe, Co—Cr, Co—Cu, Co—Pt,Co—Mn and the like are preferable. Above all, Co—Fe is most preferable.Further, if its composition is Co_(x)Fe_(1−x) (0.75≦X<1) and a Cocomposition X is not less than 75 atom %, it becomes further preferable.

[0104] A film thickness of each of the first interface ferromagneticlayer 808 and the second interface ferromagnetic layer 810 is determinedto be at least 0.1 nm or above.

[0105] It is determined that a material of at least one of the firstferromagnetic layer 806 and the second ferromagnetic layer 807 is Ni oran alloy including Ni. Furthermore, it is determined that a material ofat least one of the third ferromagnetic layer 811 and the fourthferromagnetic layer 812 is Ni or an Ni alloy. As Ni or the Ni alloy, asoft magnetic film including Ni as a component is preferable.Specifically, as a soft magnetic layer including Ni as a component,there are Ni—Fe, Ni—Fe—Mo, Ni—Fe—Nb, Ni—Fe—B, Ni—Fe—Cr—Cu, Ni—Fe—Co,Ni—Co, Ni—Fe—Co and the like. Above all, Ni—Fe is particularly superiorin the soft magnetism and most preferable. Moreover, if it is a permalloy (Ni_(x)Fe_(1−x) (0.35≦X<1)) and an Ni composition X is not lessthan 35 atom %, the coercive force can be reduced to 79 A/m (1(0e)) orbelow.

[0106] It is determined that a total film thickness of layers consistingof Ni or an alloy including Ni in the first ferromagnetic layer 806 andthe second ferromagnetic layer 807 is not less than 60% of a filmthickness of the first free magnetic layer 816. In addition, it isdetermined that a total film thickness of layers consisting of Ni or analloy including Ni in the third ferromagnetic layer 811 and the fourthferromagnetic layer 812 is not less than 60% of a film thickness of thesecond free magnetic layer 817.

[0107] The first buffer layer 801 and the second buffer layer 803 can beformed of Ta, Zr, Ti and the like. However, any other material can beused as long as it has a function of, e.g., increasing the contactbetween the underlying electrode layer 802 and the substrate 800 orbetween the pinned magnetic layer 804 and the underlying electrode layer802, and these buffer layers may not be formed in some cases.

[0108] The cap layer 813 can be formed of Ta, Zr, Ti, Al and the like.However, any other material can be used as long as it has a function of,e.g., preventing the surface of the fourth ferromagnetic layer 812 frombeing deteriorated due to exposure to air, and the cap layer 813 may notbe formed in some cases.

[0109] The underlying electrode layer 802 can be formed of Al. However,any other metal material having a small specific resistance such as Ag,Cu, Au, Pt and the like is also preferable. Additionally, any othermaterial can be used or the underlying electrode layer 802 may not beformed in some cases.

[0110] As a material of the pinned magnetic layer 804, Co, CoFe or thelike is preferable. However, any other material can be used as long asit has a magnetic characteristic which is hardly reverted with respectto an external magnetic field. Further, the pinned magnetic layer 804can be constituted by a plurality of layers. In particular, a laminatedferri type three-layer structure or a two-layer structure including theferromagnetic layer/anti-ferromagnetic layer is further preferable sinceit can positively fix its magnetization direction.

[0111] The non-magnetic layer 805 can be formed of a non-magnetic goodconductor such as Cu, Au or Ag, or a non-magnetic insulator such as anAl oxide or a Ta oxide or an Al nitride. A type using the non-conductivegood conductor such as Cu, Au or Ag is called a spin valve type GMRelement, and a type using the non-magnetic insulator such as an Aloxide, a Ta oxide or an Al nitride is called a ferromagnetic tunneljunction element. In case of the ferromagnetic tunnel junction element,after forming a film of a non-magnetic metal layer formed of, e.g., Al,its surface is oxidized or azotized by using a gap including oxygen ornitrogen, thereby forming the insulative non-conductive layer 805.

[0112] The first ferromagnetic layer 806 and the second ferromagneticlayer 807 constitute the first main ferromagnetic layer 814, and thethird ferromagnetic layer 811 and the fourth ferromagnetic layer 812constitute the second main ferromagnetic layer 815. Further, the firstmain ferromagnetic layer 814 and the first interface ferromagnetic layer808 constitute the first free magnetic layer 816, and the second mainferromagnetic layer 815 and the second interface ferromagnetic layer 810constitute the second free magnetic layer 817. The first free magneticlayer 816 and the second free magnetic layer 817 are magneticallycoupled in such a manner that directions of their magnetic momentsbecome anti-parallel to each other by the anti-ferromagnetic exchangebonding effect through the non-magnetic intermediate layer 809, and theyfunction as a free magnetic layer. The first free magnetic layer 816,the non-magnetic intermediate layer 809 and the second free magneticlayer 817 constitute the free magnetic layer 818. The pinned magneticlayer 804, the non-magnetic layer 805 and the free magnetic layer 818constitute the magneto-resistive effect portion 819 which varies theresistance due to a change in an external magnetic field anddemonstrates the magneto-resistive effect.

[0113] Description will now be given as to a method of manufacturing amagneto-resistive effect element according to a fourth embodiment.First, films of the first buffer layer 801, the underlying electrodelayer 802, and the second buffer layer 803 are formed on the substrate800. If irregularities on the upper part of the underlying electrodelayer 802 are prominent, it is good to perform a surface flatteningtreatment such as ion beam irradiation on the film surface in this step.Subsequently, films of the pinned magnetic layer 804 and thenon-magnetic layer 805 are formed. Furthermore, on the non-magneticlayer 805 are formed the first ferromagnetic layer 806, the secondferromagnetic layer 807, the first interface ferromagnetic layer 808,the non-magnetic intermediate layer 809, the second interfaceferromagnetic layer 810, the third ferromagnetic layer 811, the fourthferromagnetic layer 812 and the cap layer 813. As a result, amulti-layer thin film structure of the magneto-resistive effect elementaccording to the fourth embodiment is obtained.

[0114] It is to be noted that the advantage of the present inventiondoes not correlate with an absolute positional relationship (filmforming order) of the pinned magnetic layer 804 and the free magneticlayer 818. As to the magneto-resistive effect portion 819, the entirelyinverted structure (entirely inverted film forming order) may beadopted.

[0115] When the obtained multi-layer thin film is processed by theprocessing method described below, the magneto-resistive effect elementaccording to the fourth embodiment of the present invention can beobtained.

[0116] First, a resist which defines an underlying electrode shape isproduced on the obtained multi-layer thin film by the optical exposureor electron ray exposure technique, and all the layers in the obtainedmulti-layer thin film are processed into the object underlying electrodeshape by using the ion milling or chemical etching technique. It is tobe noted that, when the magneto-resistive effect element is a spin valvetype GMR element, the underlying electrode layer 802 is not necessaryparticularly, and this underlying electrode shape processing step is notparticularly required either.

[0117] Subsequently, a resist which defines an element shape and anelement size is produced by using the optical exposure or electron rayexposure technique, and the magneto-resistive effect portion 819 and thecap layer 813 in the multi-layer film processed into the underlyingelectrode shape are processed into the object element shape and elementsize by using the ion milling or chemical etching technique.

[0118] Then, after conducting coating using the inter-electrodeinsulating layer, the upper electrode is formed, thereby bringing themagneto-resistive effect element according to the fourth embodiment tocompletion.

[0119] Although the above has described the example that each of thefirst main ferromagnetic layer and the second main ferromagnetic layerconsists of two magnetic layers, one of the first main ferromagneticlayer and the second main ferromagnetic layer may have a one-layerstructure like the third embodiment. Moreover, if at least one layer inthe first main ferromagnetic layer is constituted by Ni or an Ni alloyand a total film thickness of layers consisting of Ni or an Ni alloy inthe first main ferromagnetic layer is not less than 60% of a filmthickness of the first ferromagnetic layer, it is possible to adopt astructure that the first main ferromagnetic layer consists of three ormore magnetic layers. Likewise, if at least one layer in the second mainferromagnetic layer consists of Ni or an Ni alloy and a total filmthickness of layers consisting of Ni or an Ni alloy in the second mainferromagnetic layer is not less than 60% of a film thickness of thesecond ferromagnetic layer, it is possible to employ a structure thatthe second main ferromagnetic layer consists of three or more magneticlayers.

[0120] It is to be noted that a material of layers other that thoseconsisting of Ni or an Ni alloy in the first main ferromagnetic layer orthe second main ferromagnetic layer is not particularly restricted aslong as it is a magnetic material, but a layer having any otheradvantage is further preferable.

[0121] Description will now be given as to a result of manufacturing alaminated ferrimagnetic thin film according to the embodiments of thepresent invention and evaluating its magnetic characteristic.

FIRST EXAMPLE

[0122] As shown in FIG. 7, a laminated ferrimagnetic thin film accordingto the first example has a superimposed structure of a thermallyoxidized silicon substrate 500/a first Ta layer 501/a first NiFe layer502/a first CoFe layer 503/an Ru layer 504/a second CoFe layer 505/asecond NiFe layer 506/a second Ta layer 507. Compositions of the NiFelayer and the CoFe layer are Ni_(0.8)Fe_(0.2) (Ni composition: 80 atom%) and Co_(0.9)Fe0.1 (Co composition: 90 atom %), respectively. As shownin the drawing, the first Ta layer 501 has a film thickness of 1.5 nm;the first NiFe layer 502, 6 nm; the first CoFe layer 503, 0.5 nm; the Rulayer 504, 1 nm; the second CoFe layer 505, 0.5 nm; the second NiFelayer 506, 6 nm; and the second Ta layer 507, 3 nm. In the firstembodiment, the thermally oxidized silicon substrate 500 is used as thesubstrate 300; the Ta layers 501 and 507, as the buffer layer 301 andthe cap layer 307; the NiFe layers 502 and 506, as the first mainferromagnetic layer 302 and the second main ferromagnetic layer 306; theCoFe layers 503 and 505, as the first interface ferromagnetic layer 303and the second interface ferromagnetic layer 305, and the Ru layer 504as the non-magnetic intermediate layer 304, respectively.

[0123] The first NiFe layer 502 and the first CoFe layer 503 constitutethe first ferromagnetic layer 508, and the second NiFe layer 506 and thesecond CoFe layer 505 constitute the second ferromagnetic layer 509. Thefirst ferromagnetic layer 508 and the second ferromagnetic layer 509 aremagnetically coupled in such a manner that directions of their magneticmoments become anti-parallel to each other by the anti-ferromagneticexchange bonding effect through the Ru layer 504. The laminatedferrimagnetic thin film according to the first embodiment is of a typethat the respective film thicknesses (magnetic moments) of the firstferromagnetic layer 508 and the second ferromagnetic layer 509 are equalto each other, and this is a structure most suitable for evaluating themagnitude of the anti-ferromagnetic exchange bonding acting between thefirst ferromagnetic layer 508 and the second ferromagnetic layer 509.

[0124] The manufacturing method will now be described. First, a film ofthe first Ta layer 501 having a thickness of 1.5 nm was formed on thethermally oxidized silicon substrate 500. Then, films of the first NiFelayer 502 having a thickness of 6 nm, the first CoFe layer 503 having athickness of 0.5 nm, the Ru layer 504 having a thickness of 1 nm, thesecond CoFe layer 505 having a thickness of 0.5 nm, and the second NiFelayer 506 having a thickness of 6 nm were formed. Furthermore, a film ofthe second Ta layer 507 having a thickness of 3 nm was formed, therebybringing the laminated ferrimagnetic thin film according to the firstembodiment of the present invention to completion.

[0125] The thin film forming apparatus used is a DC magnetron sputterapparatus including eight sputter targets each having a diameter of twoinches. A degree of vacuum in a film forming chamber was 5×10⁻⁹ Torr andan argon gas pressure during sputtering was 3 mTorr.

[0126] The thus manufactured laminated ferrimagnetic thin film was cutinto a dimension of 1 cm×1 cm, and its magnetic characteristic wasevaluated by using a vibration sample type magnetometer.

[0127]FIG. 8 shows magnetization curves of the laminated ferrimagneticthin film according to the first example. This drawing illustrates achange in magnetic moment (vertical axis) per unit film area withrespect to a change in external magnetic field (horizontal axis). As tothe external magnetic field, reciprocating scanning was carried out in arange of −395000 A/m (−5000(0e)) to 395000 A/m (5000(0e)).

[0128] From FIG. 8, the effect of reducing the magnetic film thicknessin the low magnetic field can be confirmed in the laminatedferrimagnetic thin film according to the present invention. In FIG. 8,when the external magnetic field is zero, the magnetic moment per unitfilm area is 0 T·nm. This indicates a state that directions of themagnetic moments of the first ferromagnetic layer 508 and the secondferromagnetic layer 509 become anti-parallel to each other by theanti-ferromagnetic exchange bonding acting between these layers, and themagnetic moments of the first ferromagnetic layer 508 and the secondferromagnetic layer 509 are equal to each other in this embodiment,which cancels out the magnitudes of the magnetic moments.

[0129] Moreover, when the external magnetic field is not less than244900 A/m (3100(0e)) (=saturation magnetic field (H_(S))), the magneticmoment per unit film area has a fixed value. This indicates a state thata large external magnetic field which surpasses the anti-ferromagneticexchange bonding acting between the first ferromagnetic layer 508 andthe second ferromagnetic layer 509 is applied, and orientations of thefirst ferromagnetic layer 508 and the second ferromagnetic layer 509 arealigned in the completely the same direction (magnetic field applyingdirection) (magnetic saturation state). Since the magnetic moment perunit film area in the magnetic saturation state is 11.4 T·nm, it can beunderstood that the saturation magnetic moment (M) per unit film area ofeach of the first ferromagnetic layer 508 and the second ferromagneticlayer 509 is 5.7 T·nm.

[0130] In the relational expression (J=H_(S)×M_(S)×t/2) between theanti-ferromagnetic exchange bonding energy (J) and the saturationmagnetic field (H_(S)) when the film thicknesses of the respectiveferromagnetic layers are equal to each other, M_(S)×t is indicative of asaturation magnetic moment per unit film area of each ferromagneticlayer. Therefore, the anti-ferromagnetic exchange bonding energy (J) ofthe laminated ferrimagnetic thin film according to this embodiment canbe calculated based on J=H_(S)×M/2 by using the saturation magneticfield (H_(S)) and the saturation magnetic moment (M) per unit film area.

[0131] The anti-ferromagnetic exchange bonding energy between theferromagnetic layers in the laminated ferrimagnetic thin film accordingto the first embodiment obtained based on this relational expression was7×10⁻⁴ J/m² (0.7 erg/cm²).

[0132] It is to be noted that the same advantage was obtained in thelaminated ferrimagnetic thin film using Co, Co—Pt and Co—Cr as materialsof the first interface ferromagnetic layer and the second interfaceferromagnetic layer. However, its anti-ferromagnetic exchange bondingenergy was 5×10⁻⁴ to 6×10⁻⁴ J/m² (0.5 to 0.6 erg/cm²) when an Ru filmthickness is 1 nm, which was slightly smaller than that when CoFe wasused.

[0133] In addition, in the laminated ferrimagnetic thin film using CoFeas a material of the first interface ferromagnetic layer and the secondinterface ferromagnetic layer, the large anti-ferromagnetic exchangebonding energy of 4×10⁻⁴ to 7×10⁻⁴ J/m² (0.4 to 0.7 erg/cm²) wasobtained irrespective of the composition of CoFe when the Ru filmthickness is 1 nm. However, when the Co composition is not less than 75atom %, the particularly large anti-ferromagnetic exchange bondingenergy (not less than 6×10⁻⁴ J/m² (0.6 erg/cm²)) was obtained.

FIRST COMPARATIVE EXAMPLE

[0134] As a first comparative example of the first embodiment, aconventional laminated ferrimagnetic thin film using CoFe wasmanufactured and its magnetic characteristic was evaluated.

[0135] As shown in FIG. 9, a laminated ferrimagnetic thin film accordingto the first comparative example has a laminated structure including athermally oxidized silicon substrate 700/a first Ta layer 701/a firstCoFe layer 702/a Ru layer 703/a second CoFe layer 704/a second Ta layer705. Compositions of the NiFe layer and the CoFe layer used areNi_(0.8)Fe_(0.2) (Ni composition: 80 atom %) and Co_(0.9)Fe_(0.1) (Cocomposition: 90 atom %), respectively. As shown in the drawing, thefirst Ta layer 701 has a thickness of 1.5 nm; the first CoFe layer 702,4 nm; the Ru layer 703, 1 nm; the second CoFe layer 704, 4 nm; and thesecond Ta layer 705, 3nm. This is the conventional laminatedferrimagnetic thin film in which the thermally oxidized siliconsubstrate is used as the substrate, Ta is used as the buffer layer andthe cap layer, CoFe is used as the ferromagnetic layer and Ru is used asthe non-magnetic intermediate layer.

[0136] The first CoFe layer 702 and the second CoFe layer 704 aremagnetically coupled in such a manner that directions of their magneticmoments become anti-parallel to each other by the anti-ferromagneticexchange bonding effect through the Ru layer. The laminatedferrimagnetic thin film according to the first comparative example is ofa type that film thicknesses (magnetic moments) of the first CoFe layer702 and the second CoFe layer 704 are equal to each other, and this isthe structure most suitable for evaluating the magnitude of theanti-ferromagnetic exchange bonding acting between the first CoFe layer702 and the second CoFe layer 704.

[0137] Description will now be given as to a film forming method of thislaminated ferrimagnetic thin film. First, a film of the first Ta layer701 having a thickness of 1.5 nm was formed on the thermally oxidizedsilicon substrate 700. Then, a film of the first CoFe layer 702 having athickness of 4 nm, a film of the Ru layer 703 having a thickness of 1 nmand a film of the second CoFe layer 704 having a thickness of 4 nm wereformed. Further, a film of the second Ta layer 705 having a thickness of3 nm was formed thereon, thereby bringing the laminated ferrimagneticthin film according to the comparative example 1 to completion.

[0138] The thin film forming apparatus used in this example is a DCmagnetron sputter apparatus including eight sputter targets each havinga diameter of two inches, which is equal to that used in the firstembodiment. A degree of vacuum in a film forming chamber was 5×10⁻⁹Torr, and an argon gas pressure during sputtering was 3 mTorr.

[0139] The thus manufactured laminated ferrimagnetic thin film accordingto the first comparative example was cut out into a dimension of 1 cm×1cm, and its magnetic characteristic was evaluated by using a vibrationsample type magnetometer.

[0140]FIG. 10 shows magnetization curves of the laminated ferrimagneticthin film according to the first comparative example. This drawingillustrates a change in magnetic moment (vertical axis) per unit filmarea with respect to a change in external magnetic field (horizontalaxis). As to the external magnetic field, reciprocating scanning wascarried out in a range of −395000 A/m (−5000(0e)) to 395000 A/m(5000(0e)).

[0141] From this drawing, it is possible to confirm the effect ofreducing the magnetic film thickness in the low magnetic field of thelaminated ferrimagnetic thin film according to the first comparativeexample. In FIG. 10, when the external magnetic field is zero, themagnetic moment per unit film area is 0 T·nm. This indicates thatdirections of the magnetic moments of the first CoFe layer 702 and thesecond CoFe layer 704 become anti-parallel to each other by theanti-ferromagnetic exchange bonding acting between the first CoFe layer702 and the second CoFe layer 704, and the magnetic moments of the firstCoFe layer 702 and the second CoFe layer 704 are equal to each other inthe first comparative example, thereby completely canceling out themagnitudes of the magnetic moments.

[0142] Furthermore, when the external magnetic field is not less than244900 A/m (3100(0e)) (=saturation magnetic field (H_(S))), the magneticmoment per unit film area has a fixed value. This corresponds to a statethat the large external magnetic field surpassing the anti-ferromagneticexchange bonding acting between the first CoFe layer 702 and the secondCoFe layer is applied and orientations of the first CoFe layer 702 andthe second CoFe layer 704 are aligned in completely the same direction(magnetic field application direction) (magnetic saturation state).Since the magnetic moment per unit film area in the magnetic saturationstate is 11.4 T·nm, it can be understood that the saturation magneticmoment (M) per unit film area of each of the first CoFe layer 702 andthe second CoFe layer 704 is 5.7 T·nm.

[0143] Like the first embodiment, the anti-ferromagnetic exchangebonding energy (J) of the laminated ferrimagnetic thin film according tothe first comparative example can be calculated based on J=H_(S)×M/2 byusing the saturation magnetic field (H_(S)) and the magnetic moment (M)per unit film area of each ferromagnetic layer during saturation. Theanti-ferromagnetic exchange bonding energy between the ferromagneticlayers in the laminated ferrimagnetic thin film according to the firstcomparative example obtained based on this relational expression was7×10⁻⁴ J/m² (0.7 erg/cm²).

[0144] The characteristic of the laminated ferrimagnetic thin filmaccording to the first embodiment is compared with that according to thefirst comparative example. The both magnetic films have completely thesame anti-ferromagnetic exchange bonding energy (7×10⁻⁴ J/m² (0.7erg/cm²)). It can be said that the anti-ferromagnetic exchange bondingintensity of the laminated ferrimagnetic thin film according to thefirst embodiment is as strong as that of CoFe/Ru/NiFe-based thin film.Referring to FIG. 1, when the Ru film thickness is 1 nm, theanti-ferromagnetic exchange bonding energy of the NiFe/Ru/NiFe-basedfilm is approximately 5×10⁻⁵ J/m² (0.05 erg/cm²), and the bondingintensity (7×10⁻⁴ J/m² (0.7 erg/cm²)) of the first embodiment cannot beproduced. In the laminated ferrimagnetic thin film according to thefirst embodiment, it can be said that CoFe (the first interfaceferromagnetic layer and the second interface ferromagnetic layer) havinga thickness of 0.5 nm at the Ru interface is in charge of magneticbonding. Furthermore, in the laminated ferrimagnetic thin filmsaccording to the first embodiment and the first comparative example, thesufficient magnetic bonding is obtained even in the large film thicknessthat the Ru film thickness is 1 nm. This indicates that the both thinfilms have the merit of the Co-based magnetic bonding which does notrequire precise control over the Ru film thickness (which has a largemargin with respect to the Ru film thickness).

[0145] It is to be noted that Ru was used as a material of thenon-magnetic intermediate layer in the first embodiment, but it isneedless to say that the same advantages can be obtained even if Rh, Iror Cu which gives the large anti-ferromagnetic exchange bonding energyequal to that of Ru is used as the non-magnetic intermediate layermaterial.

SECOND EXAMPLE

[0146] In the laminated ferrimagnetic thin film having the structurelike that of the first embodiment, a plurality of samples that a filmthickness of the interface ferromagnetic layer (CoFe) was changed weremanufactured, and the relationship between each film thickness when CoFewas used for the first and second interface ferromagnetic layers and theadvantage of the present invention was examined. Compositions of NiFeand CoFe used are Ni_(0.8)Fe0.2 (Ni composition: 80 atom %) andCo_(0.9)Fe_(0.1) (Co composition: 90 atom %), respectively.

[0147] Like the first embodiment, in the structure of the laminatedferrimagnetic thin film according to the second embodiment, a terminallyoxidized silicon substrate is used as the substrate 300 in the firstembodiment; Ta, as the buffer layer 301 and the cap layer 307; NiFe, asthe first main ferromagnetic layer 302 and the second main ferromagneticlayer 306; CoFe, as the first interface ferromagnetic layer 303 and thesecond interface ferromagnetic layer 305; and Ru, as the non-magneticintermediate layer 304. However, film thicknesses of the first mainferromagnetic layer 302 and the second main ferromagnetic layer 306 andfilm thicknesses of the first interface ferromagnetic layer 303 and thesecond interface ferromagnetic layer 305 are different from those in thefirst embodiment.

[0148] Film structures of the manufactured samples according to thisembodiment are as shown in Table 1. A numeric figure in parenthesesdenotes a film thickness (nm) of each layer. TABLE 1 Sample 1Substrate/Ta (1.5 nm)/NiFe (6.8 nm)/CoFe (0.1 nm)/ Ru (1 nm)/CoFe (0.1nm)/NiFe (6.8 nm)/Ta (3 nm) Sample 2 Substrate/Ta (1.5 nm)/NiFe (6.6nm)/CoFe (0.2 nm)/ Ru (1 nm)/CoFe (0.2 nm)/NiFe (6.6 nm)/Ta (3 nm)Sample 3 Substrate/Ta (1.5 nm)/NiFe (6.4 nm)/CoFe (0.3 nm)/ Ru (1nm)/CoFe (0.3 nm)/NiFe (6.4 nm)/Ta (3 nm) Sample 4 Substrate/Ta (1.5nm)/NiFe (6.2 nm)/CoFe (0.4 nm)/ Ru (1 nm)/CoFe (0.4 nm)/NiFe (6.2nm)/Ta (3 nm) Sample 5 Substrate/Ta (1.5 nm)/NiFe (5.8 nm)/CoFe (0.6nm)/ Ru (1 nm)/CoFe (0.6 nm)/NiFe (5.8 nm)/Ta (3 nm) Sample 6Substrate/Ta (1.5 nm)/NiFe (5.6 nm)/CoFe (0.7 nm)/ Ru (1 nm)/CoFe (0.7nm)/NiFe (5.6 nm)/Ta (3 nm) Sample 7 Substrate/Ta (1.5 nm)/NiFe (5.0nm)/CoFe (1.0 nm)/ Ru (1 nm)/CoFe (1.0 nm)/NiFe (5.0 nm)/Ta (3 nm)Sample 8 Substrate/Ta (1.5 nm)/NiFe (4.0 nm)/CoFe (1.5 nm)/ Ru (1nm)/CoFe (1.5 nm)/NiFe (4.0 nm)/Ta (3 nm)

[0149] The manufacturing method is also substantially equal to that ofthe first embodiment. First, films of a Ta layer having a thickness of1.5 nm, an NiFe layer having an object thickness and a CoFe layer havingan object thickness are formed on the thermally oxidized siliconsubstrate, and then films of an Ru layer having a thickness of 1 nm, aCoFe layer having an object thickness and an NiFe layer having an objectthickness are formed. Furthermore, a film of a Ta layer having athickness of 3 nm is formed thereon, thereby bringing the basicstructure of the laminated ferrimagnetic thin film according to thesecond example of the present invention to completion.

[0150] The thin film forming apparatus used in this example is a DCmagnetron sputter apparatus including eight sputter targets each havinga diameter of two inches, which is equal to that used in theembodiment 1. A degree of vacuum in a film forming chamber was 5×10⁻⁹,and an argon gas pressure during sputtering was 3 mTorr.

[0151] The thus manufactured laminated ferrimagnetic thin film accordingto the second embodiment was cut out into a dimension of 1 cm×1 cm, itsmagnetic characteristic was evaluated by using a vibration sample typemagnetometer, and its saturation magnetic field (H_(S)) and a saturationmagnetic moment (M_(S)×t) per unit film area of each of the firstferromagnetic layer 308 and the second ferromagnetic layer 309 wereobtained like the first embodiment. Moreover, like the first embodiment,the magnitude of the anti-ferromagnetic exchange bonding energy in eachsample was calculated by using the relational expression ofJ=H_(S)×(M_(S)×t)/2.

[0152]FIG. 11 shows the relationship between the interface ferromagneticlayer (CoFe) film thickness of the laminated ferrimagnetic thin filmaccording to the second example and the anti-ferromagnetic exchangebonding energy obtained in the above-described manner. It is to be notedthat FIG. 11 also shows plotted points of the laminated ferrimagneticthin film according to the first embodiment corresponding to the CoFefilm thickness=0.5 nm and plotted points of the substrate/Ta (1.5nm)/NiFe (7 nm)/Ru (1 nm)/NiFe (7 nm)/Ta (3 nm) corresponding to theCoFe film thickness=0 nm for reference.

[0153] From FIG. 11, it can be understood that the advantage appears,the anti-ferromagnetic exchange bonding between the ferromagnetic layersbecomes firm and the margin relative to the Ru film thickness becomeslarge when the film thickness of the interface ferromagnetic layer(CoFe) is not less than 0.1 nm in the present invention. It is to benoted that, when the film thickness of the interface ferromagnetic layer(CoFe) is not less than 0.3 nm, the anti-ferromagnetic exchange bondingenergy is 7×10⁻⁴ J/m² (0.7 erg/cm²), and its intensity and marginrelative to the Ru film thickness are completely the same as those ofthe CoFe/Ru/CoFe-based thin film.

[0154] In addition, from this drawing, it can be understood that thebonding intensity is 6×10⁻⁵ J/m² (0.06 erg/cm²) which is very small, andthe NiFe/Ru/NiFe-based coupling has the small bonding intensity and anarrow margin relative to the Ru film thickness when the presentinvention is not used (CoFe film thickness=0 nm).

[0155] It is to be noted that, even in the laminated ferrimagnetic thinfilm using Co, Co—Pt and Co—Cr as materials of the first interfaceferromagnetic layer and the second interface ferromagnetic layer, thefilm thicknesses of the first interface ferromagnetic layer and thesecond interface ferromagnetic layer of at least 0.1 nm or above arerequired in order to obtain the advantages of the present invention.

THIRD EXAMPLE

[0156] As a practical example (third example) of the first embodimentaccording to the present invention, a laminated ferrimagnetic thin filmwas manufactured and its magnetic characteristic was evaluated. As shownin FIG. 12, the laminated ferrimagnetic thin film according to the thirdexample has a laminated structure including a thermally oxidized siliconsubstrate 100/a first Ta layer 101/a first NiFe layer 102/a first CoFelayer 103/an Ru layer 104/a second CoFe layer 105/a second NiFe layer106/a second Ta layer 107. Compositions of NiFe and CoFe used areNi_(0.8)Fe_(0.2) (Ni composition: 80 atom %) and Co_(0.9)Fe_(0.1) (Cocomposition: 90 atom %).

[0157] In regard to a film thickness of each layer, as shown in thedrawing, the first Ta layer 101 has a thickness of 1.5 nm; the firstNiFe layer 102, 6 nm; the first CoFe layer 103, 0.5 nm; the Ru layer104, 1 nm; the second CoFe layer 105, 0.5 nm; the second NiFe layer 106,4 nm; and the second Ta layer 107, 3 nm. The thermally oxidized siliconsubstrate 100 was used as the substrate 300 according to the firstembodiment; Ta 101 and 107, as the buffer layer 301 and the cap layer307; the NiFe layers 102 and 106, as the first main ferromagnetic layer302 and the second main ferromagnetic layer 306; the CoFe layers 103 and105, as the first interface ferromagnetic layer 303 and the secondinterface ferromagnetic layer 305; and the Ru layer 104, as thenon-magnetic intermediate layer 304.

[0158] The first NiFe layer 102 and the first CoFe layer 103 constitutethe first ferromagnetic layer 108, and the second NiFe layer 106 and thesecond CoFe layer 105 constitute the second ferromagnetic layer 109. Thefirst ferromagnetic layer 108 and the second ferromagnetic layer 109 aremagnetically coupled in such a manner that directions of their magneticmoments become anti-parallel to each other by the anti-ferromagneticexchange bonding effect through the Ru layer 104. As different from thefirst or the second embodiment, the laminated ferrimagnetic thin filmaccording to the third embodiment has a difference in magnetic momentbetween the first ferromagnetic layer 108 and the second ferromagneticlayer 109. This is a structure suitable for evaluating the magneticcharacteristic when the entire laminated ferrimagnetic thin film issubjected reversion of magnetization while maintaining magnetic couplingbetween the first ferromagnetic layer 108 and the second ferromagneticlayer 109 in the low magnetic field.

[0159] First, a film of the first Ta layer 101 having a thickness of 1.5nm was formed on the thermally oxidized silicon substrate 100. Then, onthe first Ta layer 101 were formed a film of the first NiFe layer 102having a thickness of 6 nm, a film of the first CoFe layer 103 having athickness of 0.5 nm, a film of the Ru layer having a thickness of 1 nm,a film of the second CoFe layer 105 having a thickness of 0.5 nm, and afilm of the second NiFe layer having a thickness of 4 nm. Furthermore, afilm of the second Ta layer 107 having a thickness of 3 nm was formed,thereby bringing the laminated ferrimagnetic thin film according to thethird embodiment to completion.

[0160] The thin film forming apparatus used in this example is a DCmagnetron sputter apparatus including eight sputter targets each havinga diameter of two inches, which is equal to that used in the firstembodiment. A 15 degree of vacuum in a film forming chamber was 5×10⁻⁹Torr, and an argon gas pressure during sputtering was 3 mTorr.

[0161] The thus manufactured laminated ferrimagnetic thin film accordingto this embodiment was cut out into a dimension of 1 cm×1 cm, and itsmagnetic characteristic was evaluated by a vibration sample typemagnetometer.

[0162]FIG. 13 show magnetization curves of the laminated ferrimagneticthin film according to the third example. This drawing illustrates achange in the magnetic moment (vertical axis) per unit film arearelative to a change in the external magnetic field (horizontal axis).As to the external magnetic field, reciprocating scanning was carriedout in a range of −158 A/m (−2(0e)) to 158 A/m (2(0e)). In this magneticfield scanning range, anti-ferromagnetic coupling of the laminated ferriis unsaturated. It is to be noted that the saturation magnetic field ofthe laminated ferrimagnetic thin film according to this embodiment wasadditionally measured and its value was 316000 A/m (4000(0e)). Moreover,it was confirmed that the magnetic moment per unit film area at thattime is 10 T·nm.

[0163] From this drawing, the effect of reducing the magnetic thin filmin the low magnetic field of the laminated ferrimagnetic thin filmaccording to the present invention can be confirmed. That is, in FIG.13, when the external magnetic field is zero, the magnetic moment perunit film area is 2 T·nm. This indicates the state that the directionsof the magnetic moments of the first ferromagnetic layer 108 and thesecond ferromagnetic layer 109 become anti-parallel due to theanti-ferromagnetic exchange bonding acting therebetween and themagnitudes of the magnetic moments are partially canceled out. In thisembodiment, there is a difference corresponding to 2 mm of NiFe betweenthe magnetic film thicknesses of the first ferromagnetic layer 108 andthe second ferromagnetic layer 109. Since the saturation magnetization(Ms) of NiFe is approximately 1 T, the 2 T·m magnetic moment per unitfilm area observed when the external magnetic field is zero completelymatches with the designed magnetic film thickness difference. Thehysteresis shown in the drawing indicates that the entire laminatedferrimagnetic thin film is subjected to magnetization reversion with thefirst ferromagnetic layer 108 and the second ferromagnetic layer 109being magnetically coupled in the anti-ferromagnetic manner.

[0164] In addition, the reverting coercive force (which is referred toas the difference magnetization reverting coercive force (H_(C)) in thisspecification) and the reverted magnetic field are very small asapproximately 79 A/m (1 (0e)), and it can be understood that thelaminated ferrimagnetic thin film according to this embodiment issufficiently preferable as the free magnetic layer in themagneto-resistive effect element and has the excellent soft magneticcharacteristic.

SECOND COMPARATIVE EXAMPLE

[0165] As a comparative example of the third embodiment, a conventionallaminated ferrimagnetic thin film using CoFe was manufactured, and itsmagnetic characteristic was evaluated. As shown in FIG. 14, thelaminated ferrimagnetic thin film according to the second comparativeexample has a laminated structure including a thermally oxidized siliconsubstrate 120/a first Ta layer 121/a first CoFe layer 122/an Ru layer123/a second CoFe layer 124/a second Ta layer 125. Compositions of NiFeand CoFe used in this example are Ni_(0.8)Fe_(0.2) (Ni composition: 80atom %) and Co_(0.9)Fe_(0.1) (Co composition: 90 atom %), respectively.In regard to a film thickness of each layer, as shown in the drawing,the first Ta layer 121 has a thickness of 1.5 nm; the first CoFe layer122, 4 nm; the Ru layer 123, 1 nm; the second CoFe layer 124, 3 nm; andthe second Ta layer 125, 3 nm. In this laminated ferrimagnetic thin filmaccording to the second comparative example, the thermally oxidizedsilicon substrate is used as the substrate; Ta, as the buffer layer andthe cap layer; CoFe, as the ferromagnetic layer; and Ru, as thenon-magnetic intermediate layer.

[0166] The first CoFe layer 122 and the second CoFe layer 124 aremagnetically coupled in such a manner that directions of their magneticmoments become anti-parallel due to the anti-ferromagnetic exchangebonding effect through the Ru layer 123. As different from the firstcomparative example, the laminated ferrimagnetic thin film according tothe second embodiment is of a type that there is a difference inmagnetic moment between the first CoFe layer 122 and the second CoFelayer 124, and has a structure suitable for evaluating the magneticcharacteristic when the entire laminated ferrimagnetic thin film issubjected to magnetization reversion while maintaining magnetic couplingbetween the first CoFe layer 122 and the second CoFe layer 124 in thelow magnetic field.

[0167] Description will now be given as to a method of forming thislaminated ferrimagnetic thin film. First, a film of the first Ta layer121 having a thickness of 1.5 nm was formed on the thermally oxidizedsilicon substrate 120. Then, on the first Ta layer 121 were formed afilm of the first CoFe layer 122 having a thickness of 4 nm, a film ofthe Ru layer 123 having a thickness of 1 nm, and a film of the secondCoFe layer 124 having a thickness of 3 nm. Additionally, a film of thesecond Ta layer 125 having a thickness of 3 nm was formed, therebybringing the laminated ferrimagnetic thin film according to the secondcomparative example to completion.

[0168] The thin film forming apparatus used in this example is a DCmagnetron sputter apparatus including eight sputter targets each havinga diameter of two inches, which is the same as that used in the firstembodiment. A degree of vacuum in a film forming chamber was 5×10⁻⁹Torr, and an argon gas pressure during sputtering was 3 mTorr.

[0169] The thus manufactured laminated ferrimagnetic thin film accordingto the second comparative example is cut out into a dimension of 1 cm×1cm, and its magnetic characteristic was evaluated by using a vibrationsample type magnetometer.

[0170]FIG. 15 shows magnetization curves of the laminated ferrimagneticthin film according to the second comparative example. This drawingillustrates a change in the magnetic moment (vertical axis) per unitfilm area relative to a change in the external magnetic filed(horizontal axis). As to the external magnetic field, reciprocatingscanning was carried out in a range of −79000 A/m (−1000(0e)) to 7900A/m (1000(0e)). In this magnetic field scanning range, theanti-ferromagnetic coupling of the laminated ferri is unsaturated. Byadditional measurement, it was confirmed that the saturation magneticfield of the laminated ferrimagnetic thin film according to the secondcomparative example is 316000 A/m (4000(0e)) and the magnetic moment perunit film area at that time is 9.9 T·nm.

[0171] From this drawing, it is possible to confirm the effect ofreducing the magnetic film thickness in the low magnetic field like thethird embodiment.

[0172] That is, in FIG. 15, the magnetic moment per unit film area isapproximately 2 T·nm when the external magnetic field is zero. Thisindicates a state that directions of the magnetic moments of the firstCoFe layer 122 and the second CoFe layer 124 become anti-parallel toeach other due to the anti-ferromagnetic exchange bonding acting betweenthem and the magnitudes of the magnetic moments are partially canceledout. In the second comparative example, a difference corresponding to 1nm of CoFe is provided to the magnetic film thicknesses of the firstCoFe layer 122 and the second CoFe layer 124. Since the saturationmagnetization (Ms) of CoFe is approximately 2 T, the 2 T·nm magneticmoment per unit film area observed when the external magnetic field iszero matches with the designed magnetic film is thickness difference.The hysteresis shown in the drawing indicates that the entire laminatedferrimagnetic thin film is subjected to magnetization reversion whilemaintaining the magnetic coupling of the first CoFe layer 122 and thesecond CoFe layer 124 in the anti-ferromagnetic manner.

[0173] However, its reverting coercive force is 19750 A/m and itsreverted magnetic field is approximately 39500 A/m, which are very largevalues. Since the magnetic field required for magnetization reversion istoo large, the laminated ferrimagnetic thin film according to the secondcomparative example is not suitable as the free magnetic layer of themagneto-resistive effect element at all.

[0174] Based on comparison between the first embodiment and the firstcomparative example and comparison between the second embodiment and thesecond comparative example, it can be understood that theCoFe/Ru/CoFe-based laminated ferrimagnetic thin film has firmanti-ferromagnetic bonding with a large margin with respect to the Rufilm thickness but is inferior in the soft magnetic characteristicduring difference magnetization reversion and that the laminatedferrimagnetic thin film according to the present invention cansimultaneously realize firm anti-ferromagnetic bonding with a largemargin with respect to the Ru film thickness and the soft magneticcharacteristic during difference magnetization reversion.

FOURTH EXAMPLE

[0175] In the laminated ferrimagnetic thin film according to the presentinvention having the same structure as that of the third embodiment, aplurality of samples having varied ratios of the main ferromagneticlayer (NiFe) and the interface ferromagnetic layer (CoFe) weremanufactured, and the relationship between a percentage of NiFe and theadvantage of the present invention (soft magnetic characteristic) wasexamined. Like the third embodiment, the structure of the laminatedferrimagnetic thin film according to the fourth embodiment is of a typethat a thermally oxidized silicon substrate is used as the substrate 300according to the first embodiment; Ta, as the buffer layer 301 and thecap layer 307; NiFe, as the first main ferromagnetic layer 302 and thesecond main ferromagnetic layer 306; CoFe as the first interfaceferromagnetic layer 303 and the second interface ferromagnetic layer305; and Ru, as the non-magnetic intermediate layer 304. However, filmthicknesses of the first main ferromagnetic layer 302 and the secondmain ferromagnetic layer 306 and film thicknesses of the first interfaceferromagnetic layer 303 and the second interface ferromagnetic layer 305are different from those in the third embodiment.

[0176] Film structures of the manufactured samples according to thefourth embodiment are as show in Table 2. A numeric figure in eachparenthesis is indicative of a film thickness (nm) of each layer. TABLE2 Sample 11 Substrate/Ta (1.5 nm)/NiFe (3 nm)/CoFe (0.5 nm)/Ru (1 nm)CoFe (0.5 nm)/NiFe (2 nm)/Ta (3 nm) Sample 12 Substrate/Ta (1.5 nm)/NiFe(3 nm)/CoFe (0.67 nm)/Ru (1 nm)/CoFe (0.67 nm)/NiFe (2 nm)/Ta (3 nm)Sample 13 Substrate/Ta (1.5 nm)/NiFe (3 nm)/CoFe (1.0 nm)/Ru (1 nm)/CoFe (1.0 nm)/NiFe (2 nm)/Ta (3 nm) Sample 14 Substrate/Ta (1.5nm)/NiFe (3 nm)/CoFe (1.3 nm)/Ru (1 nm) /CoFe (1.3 nm)/NiFe (2 nm)/Ta (3nm) Sample 15 Substrate/Ta (1.5 nm)/NiFe (3 nm)/CoFe (1.5 nm)/Ru (1 nm)/CoFe (1.5 nm)/NiFe (2 nm)/Ta (3 nm) Sample 16 Substrate/Ta (1.5nm)/NiFe (3 nm)/CoFe (2.0 nm)/Ru (1 nm) /CoFe (2.0 nm)/NiFe (2 nm)/Ta (3nm) Sample 17 Substrate/Ta (1.5 nm)/NiFe (3 nm)/CoFe (3.0 nm)/Ru (1 nm)/CoFe (3.0 nm)/NiFe (2 nm)/Ta (3 nm) Sample 18 Substrate/Ta (1.5nm)/NiFe (3 nm)/CoFe (4.0 nm)/Ru (1 nm) /CoFe (4.0 nm)/NiFe (2 nm)/Ta (3nm) Sample 19 Substrate/Ta (1.5 nm)/NiFe (3 nm)/CoFe (6.0 nm)/Ru (1 nm)/CoFe (6.0 nm)/NiFe (2 nm)/Ta (3 nm)

[0177] By determining a film thickness of the first main ferromagneticlayer 302 as 3 nm and a film thickness of the second main ferromagneticlayer 306 as 2 nm, a difference is provided to the magnetic moments ofthe first ferromagnetic layer 308 and the second ferromagnetic layer309. Further, by varying film thicknesses of the first interfaceferromagnetic layer 303 and the second interface ferromagnetic layer 305in a range of 0.5 nm to 6 nm, a percentage of the main ferromagneticlayer (NiFe) film thickness in each ferromagnetic layer is changed in arange of 25 to 86%.

[0178] The manufacturing method is substantially the same as the thirdexample. First, a film of a Ta layer having a thickness of 1.5 nm, afilm of an NiFe layer having a thickness of an object thickness and afilm of a CoFe layer having an object thickness were formed on thethermally oxidized silicon substrate. Then, a film of an Ru layer havinga thickness of 1 nm, a film of a CoFe layer having an object thicknessand a film of an NiFe layer having an object thickness were formedthereon. Furthermore, a film of the Ta layer having a thickness of 3 nmwas formed thereon, thereby bringing the laminated ferrimagnetic thinfilm according to the fourth embodiment of the present invention tocompletion.

[0179] The thin film forming apparatus used in this example is a DCmagnetron sputter apparatus including eight sputter targets each havinga diameter of two inches, which is equal to that used in the firstembodiment. A degree of vacuum in a film forming chamber was 5×10⁻⁹Torr, and an argon gas pressure during sputtering was 3 mTorr.

[0180] The thus manufactured laminated ferrimagnetic thin film accordingto the fourth example was cut out into a dimension of 1 cm×1 cm, and itsmagnetic characteristic was evaluated by using a vibration sample typemagnetometer.

[0181] The difference magnetization reversion having the magnitude (1T·nm) corresponding to the designed magnetic film thickness difference(NiFe: 1 nm) was observed in every sample in the vicinity of the zeromagnetic field. Like the third embodiment, the difference magnetizationreverting coercive force (H_(C)) in each sample was evaluated.

[0182]FIG. 16 is a graph showing the relationship between a percentageof the main ferromagnetic layer (NiFe) film thickness in eachferromagnetic layer and the difference magnetization reverting coerciveforce (H_(C)) of the laminated ferrimagnetic thin film according to thefourth example obtained in the above-described manner.

[0183] The coercive force of NiFe (main ferromagnetic layer material) is79 A/m (1(0e)). From FIG. 16, it can be understood that the differencemagnetization reverting coercive force of the laminated ferrimagneticthin film according to the present invention is reduced to be equivalentto the coercive force of the main ferromagnetic layer material when thepercentage of each main ferromagnetic layer (NiFe) film thickness in thefirst ferromagnetic layer and the second ferromagnetic layer is at least60% or above.

[0184] It is to be noted that the similar advantage was observed in thelaminated ferrimagnetic thin film using Ni, Ni—Fe—Nb, Ni—Fe—B andNi—Fe—Co as materials of the first main ferromagnetic layer and thesecond main ferromagnetic layer, and the difference magnetizationreverting coercive force matched with the coercive force of the mainferromagnetic layer material when the percentage of the mainferromagnetic layer film thickness in each ferromagnetic layer is atleast 60% or above in any case.

[0185] The laminated ferrimagnetic thin film according to the presentinvention can simultaneously realize the ferromagnetic exchange bondingwhich has the firmness equivalent to that of the Co-based laminatedferrimagnetic thin film and has a large margin with respect to the Rufilm thickness, and the excellent soft magnetic characteristicequivalent to that of the Ni-based magnetic material.

FIFTH EXAMPLE

[0186] As a practical example (fifth example) of the second embodimentaccording to the present invention, the laminated ferrimagnetic thinfilm according to the present invention was manufactured and itsmagnetic characteristic was evaluated. As shown in FIG. 17, thelaminated ferrimagnetic thin film according to the fifth embodiment hasa laminated structure including a thermally oxidized silicon substrate200/a first Ta layer 201/a first CoFe layer 202/a first NiFe layer 203/asecond CoFe layer 204/an Ru layer 205/a third CoFe layer 206/a secondNiFe layer 207/a fourth CoFe layer 208/a second Ta layer 209. Acomposition of each of the first NiFe layer 203 and the second NiFelayer 207 is Ni_(0.8)Fe_(0.2) (Ni composition: 80 atom %). Further, acomposition of each of the first CoFe layer 202 and the fourth CoFelayer 208 is Co_(0.3)Fe_(0.7) (Co composition: 30 atom %), and acomposition of each of the second CoFe layer 204 and the third CoFelayer 206 is Co_(0.9)Fe_(0.1) (Co composition: 90 atom %). In regard toa film thickness of each layer, as shown in the drawing, the first Talayer 201 has a thickness of 1.5 nm; the first CoFe layer 202, 0.2 nm;the first NiFe layer 203, 5.6 nm; the second CoFe layer 204, 0.5 nm; theRu layer 205, 1 nm; the third CoFe layer 206, 0.5 nm; the second NiFelayer 207, 3.6 nm; the fourth CoFe layer 208, 0.2 nm; and the second Talayer 209, 3 nm. In the fifth embodiment, the thermally oxidized siliconsubstrate is used as the substrate 600 in the second embodiment; Ta, asthe buffer layer 601 and the cap layer 609; Co_(0.3)Fe_(0.7), as thefirst ferromagnetic layer 602 and the fourth ferromagnetic layer 608;NiFe, as the second ferromagnetic layer 603 and the third ferromagneticlayer 607; Co_(0.9)Fe_(0.1), the first interface ferromagnetic layer 604and the second interface ferromagnetic layer 606; and Ru, as thenon-magnetic intermediate layer 605.

[0187] The first CoFe layer 202, the first NiFe layer 203 ant the secondCoFe layer 204 constitute the first ferromagnetic layer 210, and thethird CoFe layer 206, the second NiFe layer 207 and the fourth CoFelayer 208 constitute the second ferromagnetic layer 211. The firstferromagnetic layer 210 and the second ferromagnetic layer 211 aremagnetically coupled in such a manner that directions of magneticmoments thereof become anti-parallel to each other due to theanti-ferromagnetic exchange bonding effect through the Ru layer 205. Adifference is provided to the magnetic moments of the firstferromagnetic layer 210 and the second ferromagnetic layer 211.

[0188] First, a film of the first Ta layer 201 having a thickness of 1.5nm was formed on the thermally oxidized silicon substrate 200. Then, onthe first Ta layer 201 were formed a film of the first CoFe layer 202having a thickness of 0.2 nm, a film of the first NiFe layer 203 havinga thickness of 5.6 nm, a film of the second CoFe layer 204 having athickness of 0.5 nm, the Ru layer 205 having a thickness of 1 nm, a filmof the third CoFe layer 206 having a thickness of 0.5 nm, a film of thesecond NiFe layer 207 having a thickness of 3.6 nm, and a film of thefourth CoFe layer 208 having a thickness of 0.2 nm. Furthermore, a filmof the second Ta layer 209 having a thickness of 3 nm was formedthereon, thereby bringing the laminated ferrimagnetic thin filmaccording to the fifth embodiment to completion.

[0189] The thin film forming apparatus used in this example is a DCmagnetron sputter apparatus including eight sputter targets each havinga diameter of two inches, which is equal to that used in the firstembodiment. A degree of vacuum in a film forming chamber is 5×10⁻⁹ Torr,and an argon gas pressure during sputtering is 3 mTorr.

[0190] The thus manufactured laminated ferrimagnetic thin film accordingto the present invention was cut out into a dimension of 1 cm×1 cm andits magnetic characteristic was evaluated by using a vibration sampletype magnetometer.

[0191] In the fifth example, the difference magnetization reversion of 2T·nm with H_(C)=79 A/m (1(0e)) like that in the third embodiment wasobserved. The laminated ferrimagnetic thin film according to thisexample has the excellent soft magnetic characteristic which issufficiently preferable as the free magnetic layer in themagneto-resistive effect element. Moreover, when the laminatedferrimagnetic thin film according to the fifth example is used for thefree magnetic layer in the ferromagnetic tunnel junction element, theelement MR ratio is also improved since a material with a high spinpolarization ratio comes into contact with the tunnel barrier.

[0192] It is to be noted that the difference magnetization revertingcoercive force (H_(C)) becomes 79 A/m (1(0e)) when the percentage of theNiFe layer film thickness in the first and second ferromagnetic layersis not less than 60%.

SIXTH EXAMPLE

[0193] As a practical example (sixth example) of the third embodimentaccording to the present invention, a magneto-resistive effect elementwas manufactured. The sixth example is a ferromagnetic tunnel junctionelement using the laminated ferrimagnetic thin film according to thefirst embodiment of the present invention as its free magnetic layer. Asshown in FIG. 18, the ferromagnetic tunnel junction element according tothe sixth example has a is laminated structure including a thermallyoxidized silicon substrate 150/a first Ta layer 151/an Al layer 152/asecond Ta layer 153/an IrMn layer 154/a third CoFe layer 155/a tunnelbarrier layer 156/a first NiFe layer 157/a first CoFe layer 158/an Rulayer 159/a second CoFe layer 160/a second NiFe layer 161/a Ta layer (3)162. Compositions of NiFe and CoFe used in this example areNi_(0.8)Fe_(0.2)(Ni composition: 80 atom %) and Co_(0.9)Fe_(0.1) (Cocomposition: 90 atom %), respectively. In regard to a film thickness ofeach layer, as shown in the drawing, the first Ta layer 151 has athickness of 1.5 nm; the Al layer 152, 20 nm; the second Ta layer 153,3nm; the IrMn layer 154, 10 nm; the third CoFe layer 155, 3 nm; thefirst NiFe layer 157, 3.4 nm; the first CoFe layer 158, 0.3 nm; the Rulayer 159, 1 nm; the second CoFe layer 160, 0.3 nm; the second NiFelayer 161, 2.4 nm; and the Ta layer (3) 162, 3 nm. This is the structurewhich is of a type that thermally oxidized silicon substrate is used asthe substrate 400 in the third embodiment; Al, as the underlyingelectrode layer 402; Ta, as all of the first buffer layer 401, thesecond buffer layer 403 and the cap layer 411; NiFe, as the first mainferromagnetic layer 406 and the second main ferromagnetic layer 410;CoFe, as the first interface ferromagnetic layer 407 and the secondinterface ferromagnetic layer 409; and Ru, as the non-magneticintermediate layer 408. As the non-magnetic layer 405, a tunnel barrierlayer 156 which is an insulator was used. In addition, the pinnedmagnetic layer 404 has a two-layer structure including the IrMn layer154/the third CoFe layer 155, and this element is of a type (exchangebiased type) that the magnetization direction of the third CoFe layer isfixed by a combination with the IrMn layer which is ananti-ferromagnetic body. It is to be noted that an oxide of Al was usedfor the tunnel barrier layer 156.

[0194] The first NiFe layer 157 and the first CoFe layer 158 constitutethe first free magnetic layer 164, and the second NiFe layer 161 and thesecond CoFe layer 160 constitute the second free magnetic layer 165. Thefirst free magnetic layer 164 and the second free magnetic layer 165 aremagnetically coupled in such a manner that directions of magneticmoments thereof become anti-parallel to each other due to theanti-ferromagnetic exchange bonding effect through the Ru layer 159, andfunction as the free magnetic layer. The first free magnetic layer 164,the Ru layer 159 and the second free magnetic layer 165 as a whole serveas the free magnetic layer 166. A difference is provided to the magneticmoments of the first free magnetic layer 164 and the second freemagnetic layer 165.

[0195] First, on the thermally oxidized silicon substrate 150 wereformed a film of the first Ta layer 151 having a thickness of 1.5 nm, afilm of the Al layer 152 having a thickness of 20 nm, a film of thesecond Ta layer 153 having a thickness of 3 nm, a film of the IrMn layer154 having a thickness of 10 nm, and a film of the third CoFe layer 155having a thickness of 3 nm. Then, a film of Al having a thickness of 2.2nm was formed thereon as a metal layer which can function as a tunnelbarrier layer. The pure oxygen with 0.05 mTorr was introduced in vacuo,and a tunnel barrier layer 156 was formed by an oxidizing process (100watt, 100 minutes) using a plasma gun. The introduced pure oxygen wascompletely exhausted, and the high-vacuum state was restored. Then, afilm of the first NiFe layer 157 having a thickness of 3.4 nm, a film ofthe first CoFe layer 158 having a thickness of 0.3 nm, a film of the Rulayer 159 having a thickness of 1 nm, a film of the second CoFe layer160 having a thickness of 0.3 nm, a film of the second NiFe layer 161having a thickness of 2.4 nm, and a film of the third Ta layer 162having a thickness of 3 nm were formed, thereby bringing the multi-layerthin film structure of the magneto-resistive effect element according tothe sixth embodiment to completion.

[0196] The thin film forming apparatus used in this example is a DCmagnetron sputter apparatus including eight sputter targets each havinga diameter of two inches, which is equal to that used in the firstembodiment. A degree of vacuum in a film forming chamber was 5×10⁻⁹Torr, and an argon gas pressure during sputtering was 3 mTorr.

[0197] Then, the finished ferromagnetic tunnel junction film wasprocessed into a junction element shape by using the optical exposureand electron ray exposure techniques and the ion milling technique. Thesteps will now be described with reference to FIG. 19. FIGS. 19A to 19Gare views showing the element shape manufacturing steps of theferromagnetic tunnel junction film according to the sixth example. Forsimplifying the drawings, the first Ta layer 151/the Al layer 152/thesecond Ta layer 153 in FIG. 18 are written as the underlying electrodelayer 71, and the IrMn layer 154/the third CoFe layer 155 are written asthe pinned magnetic layer 72. Additionally, the first NiFe layer 157/thefirst CoFe layer 158/the Ru layer 159/the second CoFe layer 160/thesecond NiFe layer 161/the third Ta layer 162 are written as the freemagnetic layer 74. It is to be noted that the tunnel barrier layer 156corresponds to the tunnel barrier layer 73.

[0198] First, a photoresist 75 having an underlying electrode shape wasformed by using the optical exposure technique on the multi-layer filmsurface of the sixth embodiment which had been through film formation bythe above-described method as shown in FIG. 19A, and all the layers inthe bonded film structure were processed into the wiring pattern shapeof the underlying electrode by ion milling as shown in FIG. 19B.

[0199] Then, after removing the photoresist 75, an electron beam resist76 which defines the bonding dimension was formed on the film surface byusing the electron ray exposure technique as shown in FIG. 19C, and ionmilling was applied up to the upper part of the pinned magnetic layer 72as shown in FIG. 19D.

[0200] The inter-electrode insulating layer 77 was deposited and formedwhile leaving the electron beam resist 76 as shown in FIG. 19E, andthereafter the electron beam resist 76 was removed as shown in FIG. 19F.

[0201] Alumina was used for the inter-electrode insulating layer 77.Furthermore, as shown in FIG. 19G, the respective steps of photoresistformation, deposition and formation of the Al film, and lift-off of thephotoresist were sequentially performed on the inter-electrodeinsulating layer 77 by using the optical exposure technique, therebyforming an upper electrode layer 78 having the wiring pattern of theupper electrode. This is the end of element shape processing of theferromagnetic tunnel junction film.

[0202] As to the finished ferromagnetic tunnel junction element, aresistance change in the magnetic field was measured by the directcurrent quadrupole method and the characteristic was evaluated. As thecharacteristic of the ferromagnetic tunnel junction element (unctionarea=0.052 μm²) according to the sixth embodiment, the standardizedbonding resistance was 1 M Ω μm², the MR ratio was 32%, and thereverting magnetic field of the free magnetic layer when the magneticfield was applied in the direction of 45 degrees from the magnetizationfacilitating axis was 395 A/m (5(0e)), which are very preferable for theapplication to a high density solid-state magnetic memory (MRAM) or ahigh recording density compatible magnetic head.

[0203] Incidentally, when the magnetic characteristic evaluation usingthe vibration sample type magnetometer was additionally carried out withrespect to a sample according to the sixth embodiment which had beenthrough film formation of the multi-layer film structure by theabove-described method, the difference magnetization reversion of 1 T·nmwas observed.

SEVENTH EXAMPLE

[0204] As a practical example (seventh example) of the fourth embodimentaccording to the present invention, the magneto-resistive effect elementis according to the present invention was manufactured. The seventhexample is a ferromagnetic tunnel junction element using the laminatedferrimagnetic thin film according to the second embodiment of thepresent invention as its free magnetic layer.

[0205] As shown in FIG. 20, the ferromagnetic tunnel junction elementaccording to the seventh example has a basic structure including athermally oxidized silicon substrate 900/a first Ta layer 901/an Allayer 902/a second Ta layer 903/an IrMn layer 904/a fifth CoFe layer905/a tunnel barrier layer 906/a first CoFe layer 907/a first NiFe layer908/a second CoFe layer 909/an Ru layer 910/a third CoFe layer 911/asecond NiFe layer 912/a fourth CoFe layer 913/a third Ta layer 914.

[0206] A composition of each of the first NiFe layer 908 and the secondNiFe layer 912 is Ni_(0.8)Fe_(0.2) (Ni composition: 80 atom %). Further,a composition of each of the first CoFe layer 907 and the fourth CoFelayer 913 is Co_(0.3)Fe_(0.7) (Co composition: 30 atom %), and acomposition of each of the second CoFe layer 909, the third CoFe layer911 and the fifth CoFe layer 905 is Co_(0.9)Fe_(0.1) (Co composition: 90atom %). In regard to a film thickness of each layer, as shown in thedrawing, the first Ta layer 901 has a thickness of 1.5 nm; the Al layer902, 20 nm; the second Ta layer 903, 3 nm; the IrMn layer 904, 10 nm;the fifth CoFe layer 905, 3 nm; the first CoFe layer 908, 0.2 nm; thefirst NiFe layer 908, 3.4 nm; the second CoFe layer 909, 0.3 nm; the Rulayer 910, 1 nm; the third CoFe layer 911, 0.3 nm; the second NiFe layer912, 2.4 nm; the fourth CoFe layer 913, 0.2 nm; and the third Ta layer914, 3 nm. This is the structure which is of a type that the thermallyoxidized silicon substrate is used as the substrate 800 in the fourthembodiment; Al, as the underlying electrode layer 802; Ta, as all of thefirst buffer layer 801, the second buffer layer 803 and the cap layer813; Co_(0.3)Fe_(0.7), as the first ferromagnetic layer 806 and thefourth ferromagnetic layer 812; NiFe, as the second is ferromagneticlayer 807 and the third ferromagnetic layer 811; Co_(0.9)Fe_(0.1), asthe first interface ferromagnetic layer 808 and the second interfaceferromagnetic layer 810; and Ru, as the non-magnetic intermediate layer809. As the non-magnetic layer 805, the tunnel barrier layer 906 whichis an insulator is used. Furthermore, the pinned magnetic layer 804 hasa two-layer structure including the IrMn layer 904/the fifth CoFe layer905, and this is of a type (exchange biased type) which fixes themagnetization direction of the fifth CoFe layer by being combined withthe IrMn layer as the anti-ferromagnetic material. It is to be notedthat an oxide of Al is used for the tunnel barrier layer 906.

[0207] The first CoFe layer 907, the first NiFe layer 908 and the secondCoFe layer 909 constitute the first free magnetic layer 915, and thethird CoFe layer 911, the second NiFe layer 912 and the fourth CoFelayer 913 constitute the second free magnetic layer 916. The first freemagnetic layer 915 and the second free magnetic layer 916 aremagnetically coupled in such a manner that directions of magneticmoments thereof become anti-parallel to each other due to theanti-ferromagnetic exchange bonding effect through the Ru layer 910 andthey function as the free magnetic layer. The first free magnetic layer915, the Ru layer 910 and the second free magnetic layer 916 as a wholeserve as the free magnetic layer 918. A difference is provided to themagnetic moments of the first free magnetic layer 915 and the secondfree magnetic layer 916.

[0208] First, on the thermally oxidized silicon substrate 900 wereformed a film of the first Ta layer 901 having a thickness of 1.5 nm, afilm of the Al layer 902 having a thickness of 20 nm, a film of thesecond Ta layer 903 having a thickness of 3 nm, a film of the IrMn layer904 having a thickness of 10 nm, and a film of the fifth CoFe layer 905having a thickness of 3 nm. Subsequently, a film of Al having athickness of 2.2 nm was formed as a metal layer serving as a tunnelbarrier layer. The pure oxygen with 0.05 mTorr was introduced in vacuo,and a tunnel barrier layer 906 was formed by the oxidizing process (100watt, 100 minutes) using a plasma gun. The introduced pure oxygen wascompletely exhausted, and the high-vacuum state was restored.Thereafter, a film of the first CoFe layer 907 having a thickness of 0.2nm, a film of the first NiFe layer 908 having a thickness of 3.4 nm, afilm of the second CoFe layer 909 having a thickness of 0.3 nm, a filmof the Ru layer 910 having a thickness of 1 nm, a film of the third CoFelayer 911 having a thickness of 0.3 nm, a film of the second NiFe layer912 having a thickness of 2.4 nm, a film of the fourth CoFe layer 913having a thickness of 0.2 nm, and a film of the third Ta layer 914having a thickness of 3 nm were formed thereon, thereby bringing themulti-layer thin film structure of the magneto-resistive effect elementaccording to the sixth example to completion.

[0209] The thin film forming apparatus used in this example is a DCmagnetron sputter apparatus including eight sputter targets each havinga diameter of two inches, which is the same as that used in the firstembodiment. A degree of vacuum in a film forming chamber was 5×10⁻⁹Torr, and an argon gas pressure during sputtering was 3 mTorr.

[0210] The finished ferromagnetic tunnel junction film was processedinto a junction element shape by the same steps (FIGS. 19(a) to (g)) asthose in the sixth example.

[0211] As to the finished ferromagnetic tunnel junction element, aresistance change in the magnetic field was measured by a direct currentquadrupole method, and its characteristic was evaluated.

[0212] As the characteristic of the ferromagnetic tunnel junctionelement (bonding area=0.052 μm²) according to the seventh example, thestandardized bonding resistance was 0.9 M Ω μm², the MR ratio was 39%,the reverting magnetic field of the free magnetic layer was 395 A/m(5(0e)) when the magnetic field was applied from the magnetizationfacilitating axis to the direction of 45 degrees, which are verypreferable for the application to a high density solid-state magneticmemory (MRAM) or a high recording density compatible magnetic head. Theferromagnetic tunnel junction element according to this embodiment hasthe larger MR ratio and is more preferable than the ferromagnetic tunneljunction element according to the sixth embodiment.

[0213] As described above, according to the present invention, it ispossible to readily manufacture the laminated ferrimagnetic thin filmwhich can simultaneously realize the large anti-ferromagnetic exchangebonding energy which is suitable for the laminated ferri type freemagnetic layer in the magneto-resistive effect element, and theexcellent soft magnetic characteristic of the entire magnetic layer.

[0214] While this invention has thus far been described in conjunctionwith several embodiments and examples thereof, it will be readilypossible for those skilled in the art to put this invention intopractice in various other manners.

What is claimed is:
 1. A laminated ferrimagnetic thin film, comprising:a first ferromagnetic layer; a second ferromagnetic layer; and anon-magnetic intermediate layer which is arranged therebetween and incontact with the first ferromagnetic layer and the second ferromagneticlayer, the first ferromagnetic layer and the second ferromagnetic layerbeing magnetically coupled with each other through the non-magneticintermediate layer in an anti-ferromagnetic manner, wherein the firstferromagnetic layer comprising a first main ferromagnetic layerconsisting of at least one layer, and a first interface ferromagneticlayer which is arranged between and in contact with the first mainferromagnetic layer and the non-magnetic intermediate layer, the secondferromagnetic layer comprising a second main ferromagnetic layerconsisting of at least one layer, and a second interface ferromagneticlayer which is arranged between and in contact with the second mainferromagnetic layer and the non-magnetic intermediate layer, each of thefirst interface ferromagnetic layer and the second interfaceferromagnetic layer being formed of Co or a Co alloy, each of at leastone layer in the first main ferromagnetic layer and at least one layerin the second main ferromagnetic layer being formed by a soft magneticlayer having a coercive force smaller than that of each of the firstinterface ferromagnetic layer and the second interface ferromagneticlayer, a total film thickness of layers consisting of the soft magneticlayers in the first main ferromagnetic layer being not less than 60% ofa film thickness of the first ferromagnetic layer, a total filmthickness of layers consisting of the soft magnetic layers in the secondmain ferromagnetic layer being not less than 60% of a film thickness ofthe second ferromagnetic layer.
 2. A laminated ferrimagnetic thin film,comprising: a first ferromagnetic layer; a second ferromagnetic layer;and a non-magnetic intermediate layer which is arranged therebetween andin contact with the first ferromagnetic layer and the secondferromagnetic layer, the first ferromagnetic layer and the secondferromagnetic layer being magnetically coupled with each other throughthe non-magnetic intermediate layer in an anti-ferromagnetic manner, thefirst ferromagnetic layer comprising two layers of a first mainferromagnetic layer, and a first interface ferromagnetic layer which isarranged between and in contact with the first main ferromagnetic layerand the non-magnetic intermediate layer, the second ferromagnetic layercomprising two layers of a second main ferromagnetic layer, and a secondinterface ferromagnetic layer which is arranged between and in contactwith the second main ferromagnetic layer and the non-magneticintermediate layer, each of the first interface ferromagnetic layer andthe second interface ferromagnetic layer being formed of Co or a Coalloy, each of the first main ferromagnetic layer and the second mainferromagnetic layer being formed by a soft magnetic layer having acoercive force smaller than that of each of the first interfaceferromagnetic layer and the second interface ferromagnetic layer, a filmthickness of the first main ferromagnetic layer being not less than 60%of a film thickness of the first ferromagnetic layer, a film thicknessof the second main ferromagnetic layer being not less than 60% of a filmthickness of the second ferromagnetic layer.
 3. The laminatedferrimagnetic thin film according to claim 1 or 2, wherein: thelaminated ferrimagnetic thin film is a free layer in a magneto-resistiveeffect element or a ferromagnetic tunnel element.
 4. The laminatedferrimagnetic thin film according to claim 1 or 2, wherein: thenon-magnetic intermediate layer is formed of one type of metal selectedfrom a group consisting of Ru, Rh, Ir and Cu, or an alloy having as amain component one type selected from a group consisting of Ru, Rh, Irand Cu.
 5. The laminated ferrimagnetic thin film according to claim 1 or2, wherein: the Co alloy is a Co—Fe alloy.
 6. The laminatedferrimagnetic thin film according to claim 1 or 2, wherein: the Co alloyis a Co_(x)Fe_(1−x) (0.75≦X<1) alloy.
 7. The laminated ferrimagneticthin film according to claim 1 or 2, wherein: the soft magnetic film isNi or an Ni alloy.
 8. The laminated ferrimagnetic thin film according toclaim 1 or 2, wherein: the soft magnetic film is an Ni—Fe alloy.
 9. Thelaminated ferrimagnetic thin film according to claim 1 or wherein: thesoft magnetic film is an Ni_(x)Fe_(1−x) (0.35≦X<1) alloy.
 10. Amagneto-resistive effect element, comprising: a free magnetic layer inwhich a magnetization direction is freely set with respect to anexternal magnetic field; a pinned magnetic layer including a mechanismwhich fixes the magnetization direction with respect to the externalmagnetic field; and a non-magnetic layer which is arranged between andin contact with the free magnetic layer and the pinned magnetic layer,an element resistance thereof being changed by application of anexternal magnetic field, wherein the free magnetic layer is thelaminated ferrimagnetic thin film according to claim 1 or
 2. 11. Aferromagnetic tunnel junction element, comprising: a free magnetic layerin which a magnetization direction is freely set with respect to anexternal magnetic field; a pinned magnetic layer including a mechanismwhich fixes the magnetization direction with respect to the externalmagnetic field; and a non-magnetic insulating layer which is arrangedbetween and in contact with the free magnetic layer and the pinnedmagnetic layer, an element resistance thereof being changed byapplication of the external magnetic field, wherein the free magneticlayer is the laminated ferrimagnetic thin film according to claim 1 or2.